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Thread: Diagnostics, tips, & tricks by Jim Levie (E30 Jedi Master)

  1. #1
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    Diagnostics, tips, & tricks by Jim Levie (E30 Jedi Master)

    This is a collection of all of the diagnostics, tips,and such that I've written (and pasted into threads many times). If I have errors, or have written things that need clarification, please let me know by a PM. If there are things that you'd like to see added, also let me know by a PM and I'll see what I can do. Most of what is here I wrote, but there are some things that I lifted from the Internet. Along the same lines, if you have something you'd like to discuss, on-line, start a thread and we can talk about it there.

    Also, if someone wants to contribute an article please contact me via PM. It will be published with acknowledgement of the source of the information.

    As some may know, I'm not into esthetic or stylistic subjects. But rather into making an E30 run right and perform well. While mainly aimed at cars with the M20B25 engine, a lot also pertains to E30 variants.

    Some useful on-line resources are:

    Wiring diagrams: http://wedophones.com/BMWManualsLead.htm
    BMW Illustrated Parts Breakdowns: http://realoem.com/bmw/

    ABS Diagnostics
    Alternator Diagnostics and Battery info
    Brake and Clutch Hydraulics
    Brake and Clutch Flush & Bleeding
    Check Panel Brake Warning Light
    Cooling System Bleed Procedure
    Cooling System Flush Procedure
    Differential Rebuilding
    E30 Lubricants
    Engine Cleaning
    Engine Management Diagnostics
    Excessive Parasitic Draw
    Head Gasket Leak Diagnostics
    Intermediate Shaft Bearings
    M20B25 DME Diagnostics
    OBD-1 Diagnostics
    Parking Brake Adjustment
    Rear Drive Train and Driveshaft
    Scheduled Maintenance
    SI Board Battery Replacement
    Subframe Bushings
    Suspension Check
    TPS and Idle Adjustment
    Wheel Bearings


    Now for a couple of things to illustrate the diagnostic/repair difficulties one can run into. They are rather long, but you might find them to be an interesting read.

    Engine Management Saga


    I have several PDF files covering AFM testing/repair, replacement of the clutches in an LSD, and R134a retrofit that I shamelessly scarfed from the Internet. I can't post those in this thread, but I'll happily send you a copy if you will send me a PM with an email address. I also have a few links to articles in other forums (like an auto to manual swap). I don't like to post links to other forums, but if you will send me a PM with an email address I'll send you the link.
    Last edited by richardodn; 11-25-2017 at 08:36 AM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  2. #2
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    Alternator Diagnostics and Battery info

    A simple DIY test of the alternator can be done with a DMM. At idle you should see about 13.5v and your should see about 14v at 2500rpm. The 2500rpm reading should not drop much if you load the system by turning on the headlights and the HVAC blower to high. If you don’t see those voltages the alternator isn’t working correctly.

    In many cases the cause will be worn brushes in the regulator/brush assembly. If the alternator bearings are in good condition a new regulator/brush assembly may be all that is needed.

    If you remove the alternator belt, you can check the condition of the bearings. But that isn't necessarily a conclusive test as the alternator bearings won't be under load. A simple DIY test of the alternator can be done with a DMM. At idle you should see about 13.5v and your should see about 14v at 2500rpm. The 2500rpm reading should not drop much if you load the system by turning on the headlights and the HVAC blower to high. If you don’t see those voltages the alternator isn’t working correctly.

    In many cases the cause will be worn brushes in the regulator/brush assembly. But that isn't necessarily a conclusive test as the alternator bearings won't be under load. If the alternator bearings are in good condition a new regulator/brush assembly may be all that is needed.

    If you remove the alternator belt, you can check the condition of the bearings. f the bearings are really bad, that will be apparent. The regulator can be replaced without removing the alternator from the car. When removing the belt you must loosen the pivot bolt at the bottom of the alternator. The top adjustment/lock is obvious, but if you don’t loosen the pivot bolt you’ll damage the adjuster (it it already hasn’t been damaged). If the adjuster is inop, a pry bar can be used to set belt tension.

    On an E30 another possible problem that will prevent the alternator from working is the battery warning light in the cluster. If that bulb is burned out (doesn’t come on when the ignition is switched on) it won’t supply exciter power to the alternator and thus the alternator won’t charge. At some point in the production run a resistor was added in parallel to the bulb to avoid a burned out bulb from preventing the alternator from working. But I don’t know when that happened.

    If you have to replace the alternator, do not get a generic reman (cheap) unit. Those have been known to not work out-of-the box or fail shortly after installation. Use only a genuine factory rebuilt unit. It will cost more, but it will work out of the box and likely work for a long time.

    Battery charge info:

    %chg Voltage S/G
    100 12.7 1.265
    75 12.4 1.225
    50 12.2 1.190
    25 12.0 1.155
    0 11.9 1.120

    Sulfation of batteries starts when specific gravity falls below 1.225 or voltage measures less than 12.4. Sulfation hardens the battery plates reducing and eventually destroying the ability of the battery to take and hold a charge.

    Only 30% of batteries sold today reach the 48-month mark. In fact 80% of all battery failure is related to sulfation build-up. This build up occurs when the sulfur molecules in the electrolyte (battery acid)become so deeply discharged that they begin to coat the battery's lead plates. Before long the plates become so coated that the battery dies.

    In the general case you can figure on 6 years as being the useful life of a battery, even if it has never suffered from deep discharges.
    Last edited by thejlevie; 08-30-2015 at 12:11 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    ABS Diagnostics

    The ABS system on an E30 is pretty simple. It consists of a wheel speed sensor at each wheel, and ABS module & relay above the steering column, and the ABS unit in the engine bay. It has no connections to any other parts of the car.

    If the ABS light comes on when the ignition is turned on and doesn’t go off when the engine starts the relay, module and unit are all suspect. There is a fusible link in the ABS relay that, if blown, will cause this. The fuse (a simple piece of wire) can be replaced, or better yet get a new relay. If that fails to solve the problem the ABS module or the ABS unit are the next suspects. The ABS unit contains relays that have been known to fail and can be replaced with OE parts. So you have two choices. replace the ABS module with a known good unit, or replace the relays or the entire ABS unit. I start with the ABS module.

    If the light comes on with ignition, goes out with engine start, and comes back on once the car starts moving, one (or more) of the wheel speed sensors is bad or the ABS module is bad. A simple test of the speed sensors is to disconnect all but one and see if the light comes on while driving. Since the ABS system only gets speed data from the wheel speed sensors, a good sensor will cause the light to come on as the module doesn’t see data from the other sensors. Repeat this test with each of the other speed sensors. A bad one will cause the light not to come back on as the ABS module can’t tell that the car is moving. Replace that sensor(s) and see what happens. It is possible that one or more of the input channels in the ABS module are bad.
    Last edited by thejlevie; 08-30-2015 at 01:46 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Brake and Clutch Hydraulics

    Assuming that the brake and clutch have been properly bled, when experiencing problems with the brake system (or clutch on a manual) the first check is to look for leaks at the the calipers, slave cylinder, and lines. If there are no leaks in the brake system, and especially if you experience a sinking pedal, the master cylinder is bad. The brake master cylinder can (and usually does) leak fluid into the brake booster. Check for that with a rag on the end of a wire and see if there is fluid in the bottom of the booster.

    If you find fluid in the booster, it must be replaced as brake fluid will destroy the diaphragm in the booster in short order (ask me how I know). It doesn’t matter whether you have an ATE or Girling master cylinder and booster, but both need to be from the same manufacturer. It is best to bench bleed the master cylinder before installation. Whenever I have to replace a master cylinder I’ll also replace the reservoir and seals.

    In a like manner if there are no leaks in the clutch slave, or soft line, the clutch master cylinder is bad. Usually the leak will be internal and there will be no evidence as to what is wrong. Meaning that the clutch master needs to be replaced. In the general case, the clutch master, slave, and soft line will be of the same age. So if I have to replace one part I’ll replace everything. Do it once and do it right.

    Brake calipers are pretty easy to rebuild with inexpensive kits (I get OEM parts from rmeuropean.com) or you can get rebuilt calipers. If the car has ATE calipers, replace the guide bushings and perhaps the guide pins (if corroded) when rebuilding the calipers. A little soap solution makes it easier to install the guide bushings, but otherwise no lube is needed. However, you do need to lube the seals with brake fluid.

    A little compressed air will pop the caliper pistons out. Wrap the caliper in a rag to avoid making a mess. With a caliper off, the brake system will gravity drain through the open line. I have four fittings salvaged from a wrecked car that I use to plug the lines. But a double thickness of plastic storage bag secured with rubber bands will work.

    In the rear there are four soft lines. The ones that connect to the calipers are pretty easy to replace, but the ones that go to the tee junction above the rear subframe can be a pain. High quality flare wrenches (read SnapOn or Mactools) reduce the likelihood of stripping the flare nuts. Also, liberal application of PBlaster or Kroil several days before working on the system can help. And a bit of heat from a flame wrench (MAPP or oxyacetylene) can also help.

    Top quality SS lines, like from Bimmerworld or Turner, are okay but not needed. I have seen lesser quality SS lines separate at the fitting on several occasions, but I’ve never seen an OE line fail if it was in good condition (no cracks and not ancient). I’ve used both and can’t tell any difference in brake feel. Quality SS lines are more expensive, so I only use OE/OEM soft lines now.

    Working room above the subframe is extremely limited. I usually just lower the subframe a couple of inches to get room to work. At most you will have to lower the rear of the exhaust (and support it).

    Don’t cheap out on brake/clutch parts. Get OE or OEM parts. The generic stuff has been known to fail to work out of the box or fail shortly after installation. The OE/OEM parts lasted 30+ years and you can expect them to work out of the box and continue to work for another 30 years.
    Last edited by thejlevie; 08-30-2015 at 01:46 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Brake and Clutch Flush & Bleeding

    Usually it is best do a flush and bleed at the same time as the fluid is to be changed every two years.

    A pressure bleeder, which isn’t expensive, makes this an easy one person job. One liter of ATE Type 200 fluid is more than enough for a full flush/bleed on a car with a three channel ABS. You will need about 1.5 liters on later cars with the four channel ABS system.

    The ATE fluid has proved to be resistant to moisture absorption, by testing. Which means that there is little chance of rusting or boiling of the fluid under hard braking conditions. It also has a reasonable boiling point, high enough to make it suitable for track/race use in a stock E30. Those cars with a lot more power that see the track should use Castrol SRF and change it once a year or sooner.

    Start by sucking the old fluid out of the reservoir (a turkey baster or large syringe works). Then connect the filled bleeder and pump it up to about 15psi.

    On early cars with the three channel ABS system like an E30, push a measured 200cc of fluid through each rear caliper and a measured 150cc through each front caliper. Push a measured 100cc through the clutch system on a manual transmission car.

    On later cars with the four channel ABS system, push a measured 350cc of fluid through each rear caliper and a measured 150cc through each front caliper. Push a measured 100cc through the clutch system on a manual transmission car.

    It doesn’t matter which rear wheel you start with, but the last caliper should be the left front. When the flush/bleed is finished, turn the bleeder upside down and drain fluid from the bleeder to fill the line on the reservoir and clear the hose of fluid. Then when you remove the cap from the reservoir you won’t have fluid spraying out and making a mess.

    Toss any left over fluid to avoid taking a chance on it absorbing moisture. If the brake & clutch system has no leaks you will never have to top up the system and thus have no use for the left over fluid.

    If you do spill brake fluid, wipe it up and then clean with water, or better yet spray the are with something like Simple Green and was that off with water. Brake fluid will eat up paint.

    A failure to bleed a caliper could be a plugged bleed nipple, a collapsed soft line, a pinched hard line, a bad master cylinder, or a stuck valve in the ABS unit. Cracking the line at the ABS (input and output) unit will tell where to look next. In a like manner cracking the soft line where it mates to the body lines and the caliper will narrow the search area.

    The brake master cylinder has a section for the front brakes and a section for the rear brakes. So it becomes a suspect if neither rear caliper will bleed or neither front caliper will bleed.
    Last edited by thejlevie; 08-30-2015 at 01:47 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Cooling System Bleed Procedure

    1) Using ramps or a jack get the front of the car 1' or more higher than the rear. That will make the radiator and bleed screw the highest point on the engine and facilitate removal of air.

    2) With the bleed screw open, add coolant until no more air comes out of the bleed.

    3) Leave the filler cap off, or at least loose, and set the heat for max temp and fan speed. Leaving the cap loose will prevent air that's still in the system from causing a "coolant fountain" once the engine heats up. Start the engine and allow it to warm up to operating temp. As it warms up occasionally crack the bleed screw to release any air and top up the coolant as necessary.

    4) Once the engine is at temp bring it up to 2000-2500rpm for a few seconds several times. Then crack the bleed until no more air is released. At this point the heater should be throwing lots of hot air, which indicates that the heater core is filled with coolant. You may have to repeat this a few times to get all the air out.

    5) Drive the car a bit, allow it to cool back down, and recheck the bleed for air. Over the next few days you may get very small amounts (a few bubbles) of air out of the bleed screw.

    A vacuum fill bleed system makes filling and bleeding the cooling system a trivial task. But the procedure above will work if you don’t have access to a vacuum fill system. On an E30 and some other BMW’s you can speed up the fill process by removing the small hose that runs from the coolant reservoir to the top of the radiator at the radiator end. Then fill the reservoir to the mark, screw on the cap and blow into the hose until coolant comes out of the radiator nipple. That will fill the engine and radiator with coolant pretty quickly. It may take more than one fill/blow cycle to fill the radiator. Then bleed as per above to get any remaining air out.
    Last edited by thejlevie; 08-30-2015 at 01:47 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Cooling System Flush Procedure

    If the cooling system has been properly maintained (coolant change every two years) and the coolant doesn’t look dirty, a flush is probably not necessary, A simple drain, refill, and bleed is all that is needed. Otherwise you might want to flush the cooling system. The older the car the greater the odds are that a flush will help.

    1) Get the front of the car 1-2' in the air on jack-stands.

    2) Drain the coolant at the radiator and block, if possible remove the thermostat so you will have full flow through the cooling system even if the engine is not at normal operating temperature, and set the heater controls for full hot. You can't do this on a later engine with the MAP controlled thermostat. O-ring sealed thermostats require you to make up a temporary gasket, which can be made out of pasteboard.

    3) Add flush compound and fill with plain water. Then run the engine at normal temperature as specified by the flush manufacturer (usually about 15 minutes at operating temperature). In cooler weather it may be necessary to block off some of the air into the radiator to decrease the warmup time.

    4) Allow the engine to cool until you can place your hand on the cylinder head with out discomfort. Drain the system and refill with plain water.

    5) Run the engine for 10-15 minutes or until temp is close to normal.

    6) Repeat (4) and (5) until the water drained from the system is clear and free of debris.

    7) Fill with coolant. Use BMW Blue coolant mixed 50:50 with distilled water. Tap water contains dissolved oxygen and may contain minerals. Either of which will reduce the lifetime of the coolant.

    8) Then bleed the system

    Notes:

    You don't absolutely need to remove the thermostat, but doing so will allow continuous flow through the radiator and will also make draining & filling faster and easier.

    Always allow the engine to cool to the point that you can hold your hand on the cylinder head without discomfort. That will prevent scalds from hot coolant and prevent thermally shocking the head when you dump the coolant.

    Filling the system with hot water makes the process go faster and keeps from having to run the engine a lot in a cold condition (rich mixture).

    A few ounces of Cascade dishwashing detergent is a reasonable substitute for a commercial flush compound.

    A rusty cooling system needs an oxalic acid flush. Kits for that (containing oxalic acid and soda for neutralizing the acid) used to be available, but aren’t now. Citric acid also works, but not as well on rust as oxalic acid. 6oz of oxalic acid and 4oz of soda will treat a 1-1/2 to 2-1/2 gallon cooling system. The procedure is like the above with an extra step 4 where the soda is added before the series of fill/drains are done. An engine that needs this treatment probably has a pretty severely clogged/damaged radiator and heater core, which strongly suggests that they be replaced after using this procedure on the cooling system. A cooling system that needs this treatment should have a detergent flush, the acid flush, then another detergent flush. The initial detergent flush will clean out any oil, which would interfere with the acid flush, and the final detergent flush helps to wash out loosened sediment.

    Note that the cooling system should be replaced about every 100k. There are plastic and rubber parts in the cooling system that degrade with time and can suddenly fail. As can the water pump bearings & seal. If that happens on the highway and you don’t see the rise of the temp gauge in time serious engine damage can occur. Better to replace the system on schedule than to risk a failure. Replacing the cooling system means a new radiator, fan clutch, water pump, thermostat, reservoir, cap, and all hoses. If damaged or cracked, replace the fan.

    The proper coolant is the BMW Blue coolant mixed 50:50 with distilled water. The dissolved oxygen and possible minerals in tap water will degrade the corrosion protection package in the coolant and shorten it’s life.
    Last edited by thejlevie; 08-30-2015 at 03:32 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  8. #8
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    Parking Brake Adjustment

    The correct way to adjust the parking brakes is:

    1) Lower the hand brake and loosen the cable adjusters.

    2) Working through a lug bolt hole turn the star adjuster with a flat-bladed screwdriver until the wheel locks. I just turn the adjuster until it doesn't want to turn any more. Then back off the adjuster 12 clicks. The book says 8 clicks, but I’ve had the hoes drag at that setting, so I use 12 clicks. Repeat for the other wheel. Note that the star adjuster is at the 6 o'clock position on later cars, but at the 10-11 o'clock position on an E30.

    3) Raise and lower the hand brake several times to settle the cables. Then raise the lever two or three clicks and tighten the adjusters until the wheel can just be turned with moderate force.

    If you have never had the rear rotors off, it would be a good idea to back the star adjusters all the way off and pull the rear rotors to see if the parking brake shoes are badly worn or if there are other problems in the parking brake mechanism.

    In salt rich environments it isn’t unusual to find that the backing plates have rusted out where the compression pin locks into the backing plate and the shoes aren’t being held against the backing plate. The parts to fix this aren’t expensive, but the bearing hubs have to be removed to change the plates (which means new bearings). The fronts are pretty easy, but the rear hubs are a pain if you don’t have access to a Sir Tools B90 kit.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  9. #9
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    Check Panel Brake Warning Light

    The most common problems that result in the Check Panel brake warning light being on after pressing the brake pedal with the engine running (or the light coming on while driving) will be a bad brake light switch, the wrong or aged bulbs, or corrosion in the bulb sockets.

    So when faced with this problem the first action is to make sure that you have the right bulbs with the plated bases. I get mine from my dealer to be sure I have the right ones. If the glass envelope of the bulb shows any darkening, replace it. The filament will have lost material, be of higher resistance, and trigger the warning. Be careful cleaning the sockets. A brass bristle brush is the only safe way of removing oxidation without harming the plating of the socket. If the bulbs are okay, you may need a new (OE or OEM) brake light switch.

    The way the system works is that there is a reed switch wrapped in the wire that powers the bulb. If sufficient current flows through the wire when the brake pedal is pressed the reed switch will close. All three of the brake lights have one of these reed switches and since they are wired in series all must close for the Check Panel to believe that all of the brake lights are working. That can make diagnosing this problem difficult as there is no easy way to identify which reed switch isn’t closing.

    The switches for the rear brake lights are in a module mounted in the left rear fender well, but the switch for the third brake light is a part of the light fixture.

    Bad harness contacts or wiring faults are also possibilities. And the Check Panel itself could be bad.

    In a worst case situation I’ve had to identify the brake light wire, cut it and measure current flow, and then splice it back together in order to ID the offending circuit. Then I have to figure out why the current flow is lower than normal.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    E30 Lubricants

    Our E30’s have sliding rocker arms and were designed in the days when oils with high levels of ZDDP (a lubricant for sliding surfaces) were common. Most all current oils have low ZDDP content. One story is that the ZDDP is bad for catalytic converters, though cars of that era had converters and there wasn’t a high failure rate that could be directly attributed to the ZDDP levels. Another story is that modern engines don’t have the sliding surfaces and don’t need ZDDP and ZDDP in the oil is a bit of a problem for oil recyclers. I tend to believe the latter.

    To limit rocker wear you want an oil with high levels of ZDDP. One “street” oil that satisfies this requirement is Amsoil Z-Rod 20w50, another is Shell Rotella T, though I have seen some data that suggests that Shell has lowered the ZDDP content slightly. While there are several racing oils that have higher ZDDP content, they don’t have the detergent packages as they are meant to be changed frequently, like after every event or two. Consequently they aren’t a good choice for a street car.

    I live in the south and use 20W50 year round. In cold weather (temperatures from 60 to -20F) 10W40 would be better.

    According to what I have been able to find out (bobistheoilguy.com) a Mobile-1 filter seems to be the best choice with the BMW OE or Mann filter running a close second. I have seen cheap generic filters collapse and block/limit oil flow (not a good thing).

    These engines run dirtier than modern engines and have more combustion byproducts blow by than more modern engines. That builds up in the oil and can cause gunk to form, depending on the car’s typical driving cycle. An urban cycle (lots of short low speed trips) won’t get all of the engine up to the temperatures needed to boil off the condensates and gunk will form. But a primarily rural cycle with frequent weekly trips of 20 minutes in moderate weather or 30 minutes in colder weather will get all of the engine hot enough to boil off the condensates. The nicest thing you can do for an E30 that sees a mostly urban cycle is to take it out for a 30 minute run at highway speeds once or twice a week and shorten the oil/filter change interval.

    Because of the condensates you can’t take advantage of the longer life of synthetic oil. How often to change the oil and filter is determined by your driving cycle. A purely urban cycle suggests an oil/filter change every 2500-3000 miles. A rural cycle can go to the SI service interval lights.

    I like Redline 75W90 (which contains friction modifiers) for limited slip differentials and Redline MTL 75W90 in the transmission. But a high quality ATF like Redline D4 in the transmission also works very well, especially in colder weather..

    As far as I can determine from looking at the part numbers in the BMW ETM, the internals of a G260 transmission were essentially unchanged over the production life, even though the transmissions may have a colored tag indicating what fluid to use. A factory BMW tech rep told me that the color tag was meant to indicate to a BMW tech what fluid to use to top off a transmission. He had no idea why BMW used different fluids at different points in the production run other than changes in suppliers. If you are draining the fluid and filling with fresh you can, in my opinion, ignore the tag.
    Last edited by thejlevie; 08-31-2015 at 12:16 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  11. #11
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    Engine Cleaning


    When faced with a dirty engine and/or engine bay the process I use is:

    1) Start with a hot engine and get front of the car up on jack stands. Several large pieces of cardboard under the engine area will soak up the grunge and help prevent stains.

    2) Using a putty knife, screw driver, etc., scrape off any heavy deposits. Most of that will be on the lower part of the engine and you'll have to get to it from underneath.

    3) Spray a mixture of Gunk and diesel or kerosene on using a small garden sprayer.

    4) Scrub every thing you can reach using plastic bristle brushes on painted surfaces and wire brushes on bare metal. Work heavily caked areas again with the scrapers. Spray on more solvent mixture as needed.

    5) Re-fill the sprayer with any concentrated detergent (Simple Green, pressure washer detergent, etc) and spray everything down.

    6) Using a garden hose set for a gentle spray, or better yet a plant watering wand, wash down the engine and engine bay. You want to avoid any high pressure spray as that may force water into places that you don't want it to go.

    7) Spray on more detergent and go over everything with the brushes, then repeat (6).

    8) Leave the hood open and allow the engine bay to dry for at least 8 hours before starting the engine.

    Notes: Having the engine hot will make oil and grease easier to wash off and the residual heat will help dry out any water that reaches electrical parts. You won't get the cosmoline/oil stains off the valve cover on an m20/30 engine as they are baked on. The best way to clean up the valve cover is to have it bead blasted or hot tanked, but you can get most of it off with paint remover (with the cover off the engine).
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  12. #12
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    Engine Management Diagnostics

    Idle, hard starting, and engine operation problems are most commonly caused by intake leaks and/or a sticky or defective Idle Control Valve (ICV). The only reliable method of locating intake leaks is to have a smoke test run on the intake and crank case and to test the brake booster with a gage and vacuum pump. The complete list of possible causes of an intake leak is:

    Intake boot
    Throttle body gasket
    ICV hoses & connections
    Brake booster, hoses, and connections
    Crank case breather hose
    Evaporative control hoses, valve, and expansion tank
    Fuel pressure regulator & hose
    Injector seals
    Valve cover gaskets & bungs
    Oil filler cap
    Dip stick o-rings
    Oil return tube o-rings
    Pan gasket or oil level sensor gasket

    While leaks in some of those can be found by inspection or by spraying carb cleaner on suspect areas, not finding leaks that way doesn't eliminate the possibility. Only a properly executed smoke test using the right equipment will really work. That means plugging the exhaust, replacing the AFM with a plug containing a nipple for smoke injection, and using a professional smoke machine that uses oil for long persistence smoke. Then you pressurize the intake for about 10 minutes at 2-4psi with long persistence oil smoke and watch for smoke. Note that if there is a major leak, it must be repaired and the test repeated.

    Once the possibility of intake leaks is eliminated, the ICV needs to be removed and cleaned with carb cleaner until the vane inside moves freely. When the ignition is switched on you should be able to feel vibration from the ICV. If no vibration the ICV is bad, there's a problem with its wiring or connector, there's a problem with the TPS, or the DME (or Idle Control Module (ICM) on an ETA car). Early M20B25 cars with the 153 DME are known for unstable idle problems. Replacing the 153 DME with a 173 or later fixes that and also also allows the stomp test to work.

    For the DME (or ICM) to control idle, the idle switch in the TPS must work correctly. The switch should close when the throttle stop is 1mm off the idle stop screw. Hearing a click doesn't mean the TPS is working. Check with a meter or test light by removing the back shell on connector and checking for the signals at the DME (or ICM) with the ignition on.
    Oil can, and will, get into the TPS. The switches are simple exposed metal parts and oil will interfere with the operation of the TPS. I always drill a 1/8-3/16 hole in the center of the round boss on the bottom of the TPS to provide a path for the oil to escape.

    On an ETA car the cold start valve and it’s associated sensors must be functional.

    The fuel system should be tested via the suite of tests in the Bentley manual as invalid rail pressure can be a contributor to idle and starting problems. A simple injector check is to pull the injectors, jumper the fuel relay to run the pump, and see if the injectors are leaking. You can also point the injectors into a towel, remove the coil wire, and crank the engine to see if all of the injectors appear to be spraying in a similar fashion. The best approach to possible injector problems is to have the injectors cleaned and flow tested. Since raw fuel can or will be released in these tests, have a fire extinguisher handy. I use RC Engineering for cleaning, rebuilding, and flow testing. I will always do the injectors on an an engine with 100k or more one it. A noid light will prove that each injector is seeing a firing signal.

    While a bad check valve in the high pressure pump can result in longer than normal cranking, if the fuel system is working as it is supposed to the rail will reach normal pressure in a few turns of the engine. A weak pump, clogged filter or leaking FPR in conjunction with a failed check valve can result in longer cranking and/or idle problems.

    The O2 sensor can be a contributor to idle and performance problems. The O2 sensor is a scheduled maintenance item with a useful life of no more than 60k. If the sensor has that mileage or more (or is of unknown age), replace it. A good O2 sensor is vital for proper operation of the engine. The DME uses that data to adjust fuel trim for stoic operation. An aged sensor typically indicates a leaner mixture than actually exists, which results in the engine running richer than it should.

    The ignition system can be contributor. Unless recently replaced with OE or OEM parts, install a new distributor cap, rotor, and wires. Use only OE or OEM parts. The third party (cheaper) stuff is an iffy proposition. Use NGK ZGR5A plugs as they are the closest to the original plugs that are NLA. If in doubt, replace the ignition coil with a new OE or OEM part.

    The AFM can be a contributor. If the vane doesn't move freely or the resistance track is worn the DME may be receiving invalid data from the AFM. And if someone has fiddled with the bypass air adjustment the DME may be unable to stabilize idle. The bypass air adjustment should only be adjusted per the procedure in the Bentley and with an exhaust gas analyzer. And even then everything else associated with engine management has to first be operating properly. If the AFM becomes a suspect, replacement with a good used unit is the best approach.

    Improperly adjusted or malfunctioning valves will affect idle, starting, and operation. As can compression issues from ring or cylinder wear or from the valves. A valve adjustment is called for every 15k. A useful diagnostic is to run compression (dry and wet)and leak down tests on the engine. Those tests will tell if the rings and valves are in good condition and the leak down test will usually indicate whether it is a cylinder or valve problem.

    Although not usually a problem, a bad DME temp sensor is a possibility. That generally won't cause an unstable idle, but can cause hard cold or hard hot starts and/or a rough idle. As can problems with the timing reference sensors. Although not commonly encountered, a bad harmonic balancer on an M20B25 or M30 engine will cause problems.

    When all other possibilities have been eliminated and idle, starting, or operation problems persist, replacement of the DME, or if applicable the ICM, is indicated.

    In many cases the cause of problems will be a combination of factors. So it is important to test and repair all of the possible causes.
    Last edited by thejlevie; 09-13-2015 at 07:45 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  13. #13
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    Excessive Parasitic Draw

    Normal parasitic draw on an E30 (and most other BMW’s) is 30-40ma. That is measured by disconnecting the battery ground cable and placing a DMM in current mode between the battery negative post and the ground cable. All doors and the trunk must be closed for this test.

    If you see more current draw, pull one fuse at a time to try to find the offending circuit. Then use the factory wiring diagrams at http://wedophones.com/BMWManualsLead.htm to trouble shoot that circuit. There are a few things in the car that are powered all the time (OBC, cluster, alternator, DME, and door lock module). Of those only the alternator and DME are not fused, as I recall. So if you can’t find the cause by pulling fuses, try disconnecting the alternator (it may have a bad regulator), the cluster, door lock module or the DME.

    The most popular cause of excessive draw is improperly installed aftermarket electronics and the test for that is disconnect said equipment.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  14. #14
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    Head Gasket Leak Diagnostiic

    Obviously if you have coolant in the oil or oil in the coolant the head gasket has failed and the head is probably warped. But another case is a simple loss of coolant.

    A pressure test of the cooling system will tell if there are leaks and where they are. If the test is negative on a cold engine, repeat the test on a hot engine. Occasionally one will encounter a water pump that sporadically leaks while the car is being driven, but that will leave coolant residue on the front of the engine. When running the pressure check be sure to look under the car for fluid draining from the heater core

    If testing and observation can't find leaks, the loss of coolant will be from a head gasket leak that is pumping air into the cooling system. At some point the pressure will get high enough for the cap to lift to release the pressure, which will dump some coolant. That may only happen while the car is being driven and leave no evidence as to what happened.

    The definitive test is to pressurize each cylinder for several minutes with 170-180psi while monitoring cooling system pressure with a 0-5psi gauge. A negative result on a cold engine requires the test to be repeated on a hot engine. But I have seen a couple of cases where this test didn’t work, but what follows did.

    A DIY test for a leaking head gasket is to remove the cap to vent any pressure when the engine is completely cold (like after sitting overnight). With the cap back on the hoses will be soft. Drive the car for a bit and let it completely cool down again. If the hoses are hard then, air is being pumped into the cooling system. An alternative test is to fully bleed the system, drive the car, and re-bleed. Release of a significant amount of air on a re-bleed is evidence of a head gasket leak.
    Last edited by thejlevie; 08-31-2015 at 10:47 AM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  15. #15
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    Intermediate Shaft Bearings

    The bearing part numbers are:
    11-11-1-280-863
    11-11-1-264-196

    Measure the IM shaft diameter after polishing, chuck the bearings up in a lathe, slow speed, and bore to initial size. Use a standard cam bearing installation tool and install them in the block, they will crush and become smaller than the diameter of the shaft. Hand finish with a brake cylinder hone, low speed, a little goes a long ways. Test fit and measure with a bore gauge and finish sizing with green scotchbrite. Oh yeah, make sure the front bearing lines up with the oil feed hole from the #1 main bearing feed (The second bearing does not matter as it is fed through the shaft from the front journal)

    You want about .001-.0015" clearance, I would say .002" max Anything more then that and you risk loosing too much oil pressure.

    Normal wear is the usual cause for replacing the intermediate shaft bearings. But if the block is hot tanked the bearings will be destroyed.
    Last edited by thejlevie; 08-31-2015 at 10:48 AM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  16. #16
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    M20B25 DME Diagnostics

    For an M20B25 engine to run the following conditions must be met:

    Power on DME pins:
    27 Start Input
    18 Un-switched Power input
    37 Power Input from Main Relay

    Ground on DME pins 2, 14, 19, 24

    Timing data from the CPS on DME pins 47 & 48 from a rotating engine

    To have spark power must be present at the coil positive and ground pulses from the DME's pin 1 must reach the coil negative. Power to the coil is controlled by the ignition switch via C101. When checking for spark, use the output lead from the coil to eliminate the distributor, rotor and plug wires.

    To have injector firing power must be present at each injector and ground pulses from the DME's pin 16 (Bank1) and pin 17 (Bank2) must reach the respective injector bank. Note that the injectors are wired as two banks of three. With cylinder 1,3,5 being bank 1 and 2,4,6 being bank 2. Power to the injectors is controlled by the main relay. Injector firing is best checked with a noid light.

    The fuel pump relay must have power on pin 86 (relay coil) from the main relay output (pin 87) and power on pin 30. The DME will ground pin 85 to turn on the relay and power the pump(s) via pin 87 when it sees timing data from a rotating engine. Of the above, only the fuel pump power is fused. So if the there's power at pin 87, but not at the pump, check fuse 11.

    The main relay and DME receive power from the smaller of the two wires that connect to the battery's positive terminal. That wire incorporates an in-line fuse. When the DME is presented with a start signal, it grounds the main relay pin 85 and furnishes power to the fuel pump relay, injectors, and DME. It isn’t uncommon to find that the inline fuse is corroded and not proving full power to the DME. You can cut off the heat shrink tubing and have a look at the fuse. If okay, it can be sealed and protected with several layers of good electrical tape. If the fuse is iffy or bad, I cut the fuse out, splice the wire and place a 60a lug type fuse between the small cable and the power point in the engine bay. The lug type fuse will bolt right in.

    To check these signals you will need to remove the back shell of the DME connector connector so that when appropriate the connector and the DME can be mated for tests. Some of the tests require that the DME be connected and others must be done with the DME disconnected (like continuity tests).

    Troubleshooting:

    Disconnect the battery and the DME cable. Then:

    1) Disconnect the coil negative and check continuity from that connector to DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.

    2) Check the resistance across DME 47 & 48, which should be 500-560 ohms. If the CPS is dismounted, the resistance can be seen to change from about 500 to 540-560 ohms when a ferrous object is brought to the face of the sensor. Neither pin should be grounded.

    3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel pump relay 85.

    Reconnect the coil, remount the CPS (air gap should be 1mm), plug the relays back in, reconnect the DME, and connect the battery. Then do the following checks:

    1) With the key off, verify that power is present at DME pin 18 and main relay 86 & 30.

    2) With the key on, verify that power is present at DME pin 27 and pin 18. Power to pin 18 is from the main relay and there should be power to the injectors and fuel pump relay.

    3) With the key on, verify that no voltage is present at the DME grounds (2, 14, 19, 24). All of the DME grounds are via the small bundle of brown wires that attach to the right side shock tower.

    4) Verify that power is present at the coil positive and at fuel pump relay pin 30. Those get switched power from the ignition switch via C101.

    The engine will start and run (if poorly) with only those connections to the DME in place. The other signals from Cylinder ID, AFM, temp sensor, etc., are necessary for proper operation. But they won't prevent the engine from firing.

    IMPORTANT:

    A power check means seeing a voltage within about a tenth of a volt of what you measure across the battery terminals, which should be at least 12.6v on a charged battery.

    A continuity check means seeing less that 1 ohm of resistance.

    An open circuit means seeing a resistance of at least 100k ohms.

    A good quality auto-ranging digital multimeter will make these tests much
    easier.
    Last edited by thejlevie; 09-01-2015 at 02:18 AM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  17. #17
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    OBD-1 Diagnostics

    This is only valid on a Motronic 1.1 DME (a 173 or later). It presumes that the TPS is good and properly adjusted so that both the idle and WOT signals reach the DME. To verify that this occurring, remove the backshell from the DME connector and check for the signals with the ignition on and the DME cable connected.

    Start by turning the ignition key on (do not start the engine) and pressing the gas pedal to the floor five times within a period of five seconds. If you did that correctly, then the check engine lamp will light for five seconds, then blink off, then blink on for 2.5 seconds, and then go off for another 2.5 seconds. After this, the computer will start to show you the any stored fault codes.

    The codes are given by short flashes of the check engine light, followed by short pauses. The codes are all four digit numbers. For example, the trouble fault code for monitoring the battery voltage level is 1231. This would show up flashing as "flash - pause - flash - flash - pause - flash - flash - flash - pause - flash." I suggest having a pen and paper handy when you do this, as the codes have a tendency to flash faster than you would think.

    If there is more than one fault code stored, then each code will be separated by a 2.5 second pause. When there are no more codes to be read, the computer will give the code 1000, which is one short flash, and then the light will remain off. Then the check engine light will flash a half-second and then turn off. To read the codes again, simply turn the ignition key off and on again and repeat the procedure with the gas pedal (five times within five seconds).


    Note that not all of the possible OBD-1 codes are valid for an E30 and I have marked those. Here is a table that represents all of the possibly fault codes that can be read using this method:

    Code Error Notes / Corrective Action

    1000 End of output - no more fault codes
    This code shows the end of the stream of error codes, and tell you that
    the computer is finished showing them to you.

    1444 No more faults
    This code shows that all faults have been fixed. After any faults have been
    corrected you can reset the DME by disconnecting the battery for 30 seconds.

    1211 DME Motronic Computer Fault
    This may indicate a problem with the DME computer. Most problems result
    in a dead computer that cannot give out codes, so this particular code
    is not commonly seen. If the code does appear, start and rerun the
    test for about one minute. If the code reappears, then chances are
    that you need to replace your DME computer.

    1215 Mass Air Flow Sensor Fault
    The mass air flow sensor measures the amount of air that is currently
    being drawn into the engine. A big hole in one of your fuel injection seals
    intake boot, or other places may cause the car to stall and/or generate this code.

    1216 Throttle Position Switch Fault
    The later model Motronic systems (not used on an E30) used a potentiometer
    to measure throttle position and adjust fuel levels appropriately. If the 'pot'
    is not giving off the proper values, it will produce this code.

    1218 DME Computer Output, Group #1
    These two codes can be generated when there is a ground fault short
    circuit from B+ at one of the two DME Output Amplifier Stages. This
    code is not typically seen by itself, and is usually generated with
    a host of other codes. Possible problems may be O2 sensor heater
    relay, fuel evap system problem, EKP relay, ignition coil problem,
    a faulty idle speed actuator, etc. If you get this code, disconnect
    the DME and let it sit for 15 minutes, then recheck the codes. If it
    persists, and no other problems are found, then it is probably an
    internal DME problem. If the code goes away, then ignore it and call
    it an intermittent error.

    1219 DME Computer Output, Group #2

    1221 Oxygen Sensor (primary)
    The O2 sensor measures the mixture of the car. This code is generated
    if the sensor is unplugged or broken. Sensor values are read when the
    engine warmer than 70C, and should be within 0.02 and 0.85 volts.
    Negative values indicate that the sensor needs to be replaced, and
    slow fluctuation indicate that the sensor is clogged with soot.
    Cars with catalytic converters that have been removed may push this code.

    1212 Oxygen Sensor (secondary and not present on an E30)

    1222 Oxygen Sensor Lean/Rich Detect (primary)
    If the signal from the O2 sensor indicates a very lean or very rich
    mixture for more than 10 seconds, then the computer generates this
    code. It could mean a faulty O2 sensor, a problem with another
    component, or intake leaks.

    1213 Oxygen Sensor Lean/Rich Detect (secondary and not present on an E30)

    1223 Coolant Temperature Sensor
    Measures the temperature of the coolant inside the engine block. Used
    to determine if the engine is warm or cold. Check the wiring and the
    expected resistance value of the sensor.

    1224 Intake Air Temperature Sensor
    Measures the temperature of air entering into the engine's fuel
    injection system, and adjusts the mixture accordingly. Colder air
    is more dense than warmer air and needs to be compensated for. On an E30
    the sensor is part of the AFM

    1225 Knock Sensor #1 (not present on an E30)
    The knock sensor is used to detect pre-ignition that can damage the
    engine. If the knock sensor is triggered, it will back off the timing
    of the car, reducing the 'pinging.' A fault is generated if there is
    an open circuit, a ground fault, or if the sensor sends multiple signals
    that don't correspond to proper engine operation.

    1226 Knock Sensor #2

    1227 Knock Sensor #3

    1228 Knock Sensor #4

    1231 Battery Voltage / DME Relay Monitor
    Monitors the condition of the battery and charging system, and produces
    a fault if a component goes out of specification or fails.

    1232 Throttle Idle Position Switch
    On older Motronic systems, this switch was used along with the wide
    open position switch as a primitive throttle position switch.

    1233 Throttle Wide Open Switch See above.

    1234 Speedometer "A" Signal
    This code is generated when the engine is under load, over 2500 RPM
    and no discernable speedometer signal can be detected for more than
    10 seconds. Check the wiring harness, and also the instrument console.
    Only very late E30 DME’s route the vehicle speed signal to the DME.

    1237 A/C Compressor cutoff The compressor is automatically turned off when
    accelerating from low speed under full throttle. This code indicates
    a fault in the cut-out circuit or its wiring.

    1241 Mass Airflow Sensor Codes
    1241 and 2241 can be incorrectly generated on 1992 and later models.
    The actual fault is a improperly operating idle air valve, and the
    need for an updated EPROM. See BMW bulletins for more details. This doesn’t
    apply to an E30.

    1242 A/C Compressor Signal
    This code is generated if there is a ground fault (short circuit) or
    if the system detects that the compressor unit is disconnected.

    1243 Crankshaft Position Sensor
    This code is triggered when the crank angle sensor is disconnected, or
    generates a signal that is not accurate when compared to the other
    engine sensors. On an E30 the engine won’t run without timing reference data,
    so this code is rarely, if ever seen.

    1244 Camshaft Position Sensor (not present on an E30)
    Displayed when the signal from the camshaft pulse generator is out of
    spec or absent. May indicate a problem with the injector side of the
    DME output stage.

    1245 AEGS Intervention Electronic Transmission
    Many later BMWs are equipped with electronic transmissions. If the transmission
    encounters a major problem, it will generate an emergency message, and
    your on-board computer should show "TRANSMISSION EMERGENCY PROGRAM."
    Ignition timing will retard when this program is run and the transmission will go
    into “limp” mode locked in third gear. You won’t see this on an E30.

    1247 Ignition Secondary Monitor

    1251 Fuel Injector #1 (single or group)
    Check the injector or injector group for proper wire harness
    connectivity. Also check the injectors for a clear, wide stream pattern.
    Code 1283 (Fuel Injector Output Stage) may also be triggered in
    conjunction with this code.

    1252 Fuel Injector #2 (single or group)

    1253 Fuel Injector #3

    1254 Fuel Injector #4

    1255 Fuel Injector #5

    1256 Fuel Injector #6

    1257 Fuel Injector #7

    1258 Fuel Injector #8

    1261 Fuel Pump Relay Control
    This code is generated when there is a break or ground fault in the
    circuitry associated with the DME fuel pump relay. Check pin #3 of the
    DME or the output stage in the DME (DME version M1.3 only).

    1262 Idle Speed Control
    This shows up if the idle speed actuator shows a ground fault, or if the
    car stalls from an idle above 600 RPM.

    1263 Fuel Tank Evaporative System (EVAP)
    The fuel tank evaporative system has a purge control valve that generates
    this code if there is a short circuit or open connection
    (DME version M1.3 only).

    1264 Oxygen Sensor Heating Element
    This code is triggered if there is an open circuit or a short within
    the oxygen heating element circuit. Check the O2 heating element relay
    and also the air pump relay.

    1265 Check Engine Lamp
    If the lamp in the dashboard burns out or shorts to ground, then this
    code is generated. Codes can then only be retrieved on a 173 or later DME with
    a diagnostic system.

    1266 VANOS System (not present on an E30)
    Check the wiring or the relay associated with the VANOS system (variable
    camshaft adjustment).

    1267 Air Pump Relay Control (not present on an E30)
    Check the air pump relay and wiring (were applicable).

    1271 Ignition Coil #1 (not likely to be seen on an E30)
    An open-circuit or ground fault in the ignition wiring has occurred with
    an ignition coil. Place a timing light on the coil wire and check
    for a signal. Also check the wires for faults, and check the spark plugs
    too.

    1271 Ignition Coil #2

    1271 Ignition Coil #3

    1271 Ignition Coil #4

    1271 Ignition Coil #5

    1271 Ignition Coil #6

    1271 Ignition Coil #7

    1271 Ignition Coil #8

    1281 DME Memory Unit Supply
    This indicates a fault with the internal memory of the DME computer.
    This is sometimes caused by low battery voltage. Delete the codes, and
    disconnect the DME for 15 minutes. Then reconnect, let the car idle for
    five minutes, and then drive over 30 mph for more than five minutes.
    Recheck the codes - if it occurs again, the DME is faulty and should be
    replaced.

    1282 Fault Code Memory
    This code occurs when the DME generates a set of conflicting codes.
    Disconnect the DME for 15 minutes, reconnect, and then simulate a fault
    code, like unplugging the air flow sensor or idle actuator. If the code
    reoccurs, then you will need to replace the DME.

    1283 Fuel Injector Output Stage
    This code is generated when there is a short circuit or open connection
    between the wiring from the DME to an injector or injector bank.

    1284 Knock Control Test Pulse (not present on an E30)
    The ECU periodically checks the knock sensor circuitry by sending a test
    pulse through the system. This code indicates that a test was performed,
    but no pulse was registered. Check the wiring and knock sensors.

    When you are finished reading the codes, you can reset the computer and clear them all out. Make sure that the last code (1000) has occurred, and then press down on the gas pedal for more than 10 seconds. This should clear out the memory of the DME. Repeat the fault code reading process, and the computer should generate code 1444, which means that there are no faults stored. You can also reset an E30 DME by disconnecting battery for 30 seconds, which is what I do.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  18. #18
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    Rear Drive Train and Driveshaft

    Any E30 with 150k on it (or more) could well have worn drive shaft u-joints, a worn CSB, a bad guibo. or worn half shafts (especially if the half shaft boots are torn/cracked). Wear in those parts can cause vibration or jerky acceleration and/or noise in the lower gears.

    The guibo and CSB can be visually inspected. But to assess the condition of the drive shaft it must be checked while out of the car. Any motion or binding in the u-joints is cause for replacement. Rebuilt drive shafts typically come with a new CSB installed and aren’t all that expensive. I like those from Drive Line Service of Portland.

    You should also check the differential mounting bolts, the condition of the differential bushing, and the half shafts.

    Many cars came with a harmonic balancer surrounding the gumbo, which makes it difficult to remove the guibo. Whenever I encounter one of those I don’t bother to put it back on and have never had any problems.

    If the half shafts are otherwise in good condition, the boots can be replaced pretty cheaply. Use only BMW OE parts as the aftermarket parts aren’t the right shape and will rub on the shocks. The OE kits will come with the boots grease, covers, sealant, etc. It is a bit of a dirty job, but not that difficult.

    A worn differential can also cause clunks and/or noise. They can be rebuilt, but that is a little pricey. A good used lower mileage differential will be cheaper.
    Last edited by thejlevie; 09-07-2015 at 12:36 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  19. #19
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    Scheduled Maintenance

    There are several things on an E30 (or most any other BMW) that have scheduled maintenance intervals. While many cars will go further than the scheduled intervals, The car will run better, be more reliable, and be more fun to drive is maintenance is done on schedule

    Valve adjustments: Every 15K.

    Brake/clutch fluid: Every other year. I use ATE Type 200 for brake fluid. It is the same fluid as ATE Blue sans dye and won’t stain the reservoir. I have another article on flushing/bleeding the brake system. ATE fluid has a low rate of moisture absorption and a reasonably high wet/dry boiling point. See my article on brake flushing and bleeding for a good procedure.

    Coolant: Every other year. Use BMW Blue coolant mixed 50:50 with distilled water. Tap water contains dissolved oxygen and may contain minerals that will decrease the life of the corrosion protection package in the coolant. I have another article on properly bleeding the cooling system.

    Timing belt & tensioner: Every 50k or five years

    Cooling system: Every 100k (every other timing belt change). This means replacing the radiator, fan clutch, water pump, thermostat, expansion tank & cap, and all hoses. The plastic parts degrade with age & heat and can suddenly and completely fail. If the engine fan has cracks or other damage it should also be replaced. If a major cooling system failure occurs at highway speeds and you don’t immediately park the car there is a real risk of engine damage.

    O2 sensor: The O2 sensor should be replaced every 60k. It plays a critical role in setting fuel trim. Typically as the sensor ages it indicates a leaner condition than actually exists. This results in high HC in the exhaust, is bad for fuel economy, and can damage the catalytic converters from overheating.

    Transmission & differential fluids: Every 50k (along with the filter) for an auto and about 100k for a manual.

    Ignition system: Every 150k. The wires, distributor, and rotor degrade with time and result in weak (or even no spark) conditions. The symptoms may be be very subtle (or not even noticeable), but they will affect performance. Use only BMW OE or OEM parts. Since the original plugs are NLA, the best choice now is NGK ZGR5A plugs.

    Brake caliper & soft lines: Every 150k. The calipers are easy to rebuild and the parts are cheap. I’ve seen enough failures of SS lines that I now only use BME OE soft lines. Better to rebuild the brake system on schedule than risk a loss of braking.

    Suspension: there is no hard and fast rule for replacing suspension components other than the shocks/struts. Shocks have a more limited life than will be apparent from the way the car feels as the wear is gradual. Figure on about 60k for OE type shocks and perhaps 80k from Bilsteins. Koni SA shocks will go a lot further as rebound can be adjusted to compensate for wear. Upper strut/shock mounts can only be assessed for wear out of the car, but they will normally outlast the shocks. When replacing shocks, just replace the upper mounts and you won't have to worry about them. The rear shock mounts on an E30 are a weak item. I always replace them with uprated mounts from Rouge Engineering or the ones Bimmerworld sells. Suspension bushings, motor, transmission, should probably be replaced at 150k or sooner if wear or cracks are evident. I have an article on how to inspect the suspension.
    Last edited by thejlevie; 09-13-2015 at 07:46 PM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  20. #20
    Join Date
    Dec 2004
    Location
    Huntsville, AL
    Posts
    25,923
    My Cars
    87 325is
    Subframe Bushings

    Rear subframe bushings can be a royal pain to replace. In many cases the aluminum sleeve will have corroded and be stuck in the body, especially if the bushings have never been changed or the car has lived in a salt rich area. Subframe bushing are good for no more than 150k, and usually should be replaced sooner. Bad subframe bushing can cause rear wheel alignment errors and increased NVH. The alignment errors mean that the rear tires wear quicker than they should and handling can be affected.

    With the rear of the car up in the air and the subframe supported by a floor jack under the differential start by removing the rear seat, then removing the subframe bolt nuts and support bracket. Then using a good sized sledge or air hammer drive the subframe bolts up and out. The upper end of the subframe bolts are knurled and just drive in.

    The next task is to get the subframe lowered. In some cases a pry bar will suffice. But sometimes you will have to thread a long lag bolt into the aluminum sleeve and pound from above to drive the sleeve out. It can help to spray PBlaster or Kroil down into the holes for the subframe bolts and allow several days for it to penetrate before trying to drop the subframe.

    The easiest way of removing and installing the subframe bushings is with a Sir Tools BMW3026 kit. The subframe need not be removed from the car to do that, just lowered. But that is a touch pricey for a one time job. You can burn out the old bushing. but I would only do that with the subframe out and away from the car. If you don’t have the Sir Tools kit you will have to come up with something to push the new OE/OEM bushing back in.

    Clean the pocket where the sleeve goes and lube the sleeve with anti-seize. A homemade “flap” tool driven by an electric drill and crocus cloth does a good job. Then lift the subframe back into place, drive the bolts back down, and install the support bracket and nut. Having the subframe bolts out of the way makes this a much easier task. It isn’t necessary to drive the subframe bolts all the way home. As long as you have enough of the knurl engaged to keep the bolt from turning you can pull the bolt home with nuts.

    The OE subframe bushings are fine, but poly works well and they are easier to install. I’ve never been able to tell any difference w/respect to NVH when using poly bushings.

    If aged, this is a good time to replace the soft lines above the subframe. It is also a good time to replace the differential mount bushing and rear trailing arm bushings. AKG has an inexpensive tool for the RTABs that makes replacement easy.

    A flap tool can be made by taking a piece of 1/4” or better yet 3/8” rod and cutting (read hacksaw) a slot in the end. The slide in a piece of 2” wide crocus cloth several inches long. Stick the tool into the sleeve recess and then spin the drill. It will work pretty fast and get down to bare metal quickly.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  21. #21
    Join Date
    Dec 2004
    Location
    Huntsville, AL
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    25,923
    My Cars
    87 325is
    Suspension Check

    To check control arm ball joints, squeeze the joint with a large (as in 24") pair of channel locks and pry on the joint. Any motion whatsoever in a ball joint is cause for replacement. Check the control arm bushings by prying on them with a 24" pry bar. More motion than there should be (this is where experience comes in play) or any cracks are cause for replacement. On the front control arms I prefer the OE M3 offset bushings. That increases caster and yields better high speed stability.

    Changing the control are bushings is really a press job. There are DIY ways to get the old bushing out and force in the new bushing. But for me that is an option of last resort. I prefer having a shop use their press. It is about a 15-20 minute job and if you make an appointment ahead of time you’ll be in and out quickly. Use soap as a lubricant for th control arm bushings and the rear trailing arm bushings.

    The control arm bushing brackets can be locked down while the front wheels are off the ground. Then get the car back on the ground before the soap lube has a chance to dry. It is important to wait to lock down the rear trailing arm bushings until the car is resting on the wheels. The rear suspension of an E30 isn't adjustable. Worn trailing arm bushings or bad subframe bushings will result in improper alignment of the rear wheels. In addition to degraded handling, problems there will accelerate wear of the rear tires.

    With the car up in the air, grab each front wheel at 9 & 3 o'clock and try to wiggle the wheel. Motion along that line will be worn tie rods. Not the that there is an inner (under the dust cover) and outer tie rod ball joint. Either or both can be worn. Motion when wiggling the wheel at 6 & 12 o'clock will be bearings or control arm ball joints. Spin each wheel and listen for roughness in the bearings. If the brakes drag, remove the pads or caliper (and on the rear wheels the parking brake shoes) to eliminate sounds from dragging brakes. Any roughness when spinning the wheel is cause for bearing replacement.

    Although only front toe is adjustable on an E30, a four wheel alignment will tell if there are camber or caster errors. Those errors can be the result of worn parts, bent parts, or frame damage. A single curb strike can result in damage.
    Last edited by thejlevie; 08-31-2015 at 11:42 AM.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  22. #22
    Join Date
    Dec 2004
    Location
    Huntsville, AL
    Posts
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    My Cars
    87 325is
    TPS and Idle Adjustment

    The TPS and idle speed should only be adjusted once the engine management system is operating properly. With the engine at normal operating temperature, disconnect the ICV and use the idle stop screw for an engine speed of 950rpm. Then adjust the TPS so that the idle switch closes (as measured with a DMM) when the idle stop arm is 1mm off the idle stop screw. When you reconnect the ICV the idle speed should drop to 750rpm.

    The best check for the idle (and WOT) switches in the TPS is done by removing the back shell from the DME connector and checking to see the proper inputs to the DME. That eliminates wiring as being a problem. After all, what is important is that the DME see those signals.

    Oil can, and will, get into the TPS. The switches are simple exposed metal parts and oil will interfere with their operation. I always drill a 1/8”-3/16” hole in the center of the round boss on the bottom of the TPS to provide a path for the oil to escape.

    Obviously, the idle switch is important for idle speed control as the DME won’t go into idle mode and operate the ICV if that signal isn’t reaching the DME. The WOT switch is equally important as it tells the DME to ignore O2 sensor data and to switch to wide open throttle maps, which will have a big affect on performance. Also note that above 4500rpm, when the AFM flap is all the way open the DME will be running in open loop mode using only engine temperature and rpm for fuel and spark advance if it sees the WOT switch signal.

    As a side note, both the idle and WOT switches must function for the “stomp” test to work on a 173 or later DME.

    IMPORTANT: Don’t mess with the idle air bypass screw in the AFM. It’s purpose is to set a specific CO level in the exhaust at idle. Adjusting the screw requires that the engine be operating properly and at normal operating temperature. The CO level of the exhaust is monitored and the bypass screw adjusted. This adjustment was made at the factory and should not be futzed with. If in doubt, get another AFM that still has the bypass screw sealed.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  23. #23
    Join Date
    Dec 2004
    Location
    Huntsville, AL
    Posts
    25,923
    My Cars
    87 325is
    Wheel Bearings

    Replacing the front wheel bearings is pretty easy, though you might need a bearing puller to get the inner bearing race off. You will need new lock plates and nuts and should get new dust covers. Best to use only OE or OEM parts. The cheaper stuff frequently suffers from early failure, perhaps as quickly as a year. The OE stuff generally lasted 30+ years, so it is worth the extra cost. Don’t bother with replacing the bearings in the old hub, just get a new hub and bearing assembly.

    Start by removing the dust cover and using a narrow chisel or screwdriver to bend back the lock tabs. Then remove the nut. The torque spec is 210ft-lb, so I use a 3/4” breaker bar, socket, and cheater and my body weight. A 3/4” 600ft-lb impact wrench works even better. Then simply pull the hub off. If you are lucky you won’t need to use a puller to remove the outer race of the inner bearing.

    Clean the spindle up and slide on the new hub/bearing assembly. Then the lock plate and nut. I don’t have a torque wrench that goes that high and the exact torque isn’t that critical. I use my body weight at an appropriate distance out on the breaker bar & cheater to get close (with the car on the ground, the parking brake set and the transmission in first gear. You can also use wheel chocks Then drive in the locking lugs, reinstall the dust cover and you are done.

    While the hub is off, take a good look at the inner brake dust/water shield. It is easy to replace with the hub off. Likewise for the rear shields.

    The rear wheel bearings are a whole different matter. Again, use OE or OEM parts, new lock rings and nuts. Once you have the nut off, pry out the lock ring, and drive out the half shaft using a brass drift to avoid damage to the threads on the half shaft. Obviously you will have first disconnected the inner side of the half shaft from the differential output flange. Sometimes the half shaft will come out easily and other times it can be a bear. When possible I get a helper to hold the drift and use a 16lb sledge. If it comes out easily (like with one whack) life is good, but otherwise I’m already set up for a stubborn half shaft.

    There are two schools of thought on how the lock rings go in. The cars that I have worked on that have had the original bearings had the lock rings installed under the nut, as shown in the BMW ETK. Others claim that the lock ring should go over the nut. I install the lock rings first, per the ETK and then the nut.

    Once you have the half shaft out, clean the splines carefully and examine the splines for evidence of galling. If the splines are galled you will probably not be able to get the half shaft back in and will need a new hub and half shaft. Again, only use OE/OEM parts as they will fit correctly. Good used parts are also an option. There is no way to drive the half shaft back in without damaging the outer CV joint dust cover. So it has to just slide in. On occasion I have had to use liquid nitrogen or dry ice & alcohol to shrink the splines and a heat gun to get the hub up to about 300F to get the half shafts in. A bit of anti-seize on the splines is a very good idea.

    If the CV joints are in good condition, now would be a good time to replace the grease and dust boots. After trying some aftermarket parts I went back to only OE/OEM parts. The aftermarket stuff will work, but the outer boot isn’t quite the right shape and will rub on the shock. The OE parts aren’t that expensive and come with everything needed. It is something of a messy job but otherwise pretty easy. There are a couple of variants in the boot kits, get your BMW parts guy to help figure out which you need.

    The right way to replace the bearings is with Sir Tools B90 kit. But for a single use it is really too pricey. The second best way is to remove the hubs from the car and take them to a machine shop and have the shop press in/out the bearings. At a shop this is a 15-20 minute job. If you arrange an appointment ahead of time you will be in and out in no time.

    The last option, which I don’t recommend, it to use a hefty bearing puller. Those bearing are usually in quite tightly and are thus difficult to remove with a bearing puller or slide hammer. In a pinch you can punch out the inner races and hit the outer race 4-6 times with MIG torch laying down short (~1/4” beads). That will shrink the race slightly and usually allow it to be removed.

    Some folks have used a Dremel to cut the race almost all the way through and then crack it with a chisel. But that runs the risk of damage to the hub, which is pricey. Go with option 1, ,2, or 3 first. If worn at all, I’ll use new BMW OE bolts for the connection between the half shaft and differential. While the bolts can be removed with a socket and hex key driver, an impact wrench works much better and much easier. You really don’t want to have to deal with a stripped allen later. Also use a high quality hex driver and hammer it in to make sure it is fully seated.

    While doing this job, you have an excellent opportunity to replace the rear trailing arm bushings. On a street car I use the OE/OEM rubber bushings. You can upgrade to poly bushings, which is a good thing for track car, but the poly bushings loose lube and can become noisy on the street (especially in cold weather.) The one time I used poly bushing on a street car I found it necessary to disassemble and re-lube the bushings every year, On the street there was no noticeable difference between the OE and poly bushings. AKG offers a reasonably priced RTAB tool (~$30 as I recall) that makes R/R of the bushings quite easy. Or you can have a shop do it, but the cost will be the same or higher than the tool.

    The torque for the rear half shaft nuts is 150ft-lb. I use the same procedure as for the front wheel bearing nuts.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  24. #24
    Join Date
    Dec 2004
    Location
    Huntsville, AL
    Posts
    25,923
    My Cars
    87 325is
    Differential Rebuilding

    Except for replacing clutches in an limited slip differential, rebuilding a diff is much more than just replacing parts. The backlash and pinion depth setting on the ring/pinion gear must be set with shims using a dial indicator and bluing compound and the preload on the input shaft must be set with a torque wrench. I once found a generic procedure for doing all of this, but I have lost the link. For most folks, having a pro do the work (like diffsonline.com) or finding a used unit in better condition is a more appropriate choice.

    As best I can determine, the specs are:

    Backlash .06-.14mm (.0024-.0055in)
    Pinion Preload ~.20nm (21-28in-oz).
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  25. #25
    Join Date
    Dec 2004
    Location
    Huntsville, AL
    Posts
    25,923
    My Cars
    87 325is
    SI Board Battery Replacement

    Replacing the SI board batteries isn’t too difficult. You will need a needle type soldering iron, some solder wick, small electronic cutters, a pair of small electronic needle nose pliers, and some rosin filled small diameter solder.

    Before attempting to replace the batteries take a critical look at the SI board for any signs of corrosion from leaking batteries. If you find corrosion, don’t bother to replace the batteries and get another corrosion free or new SI board.

    The easiest way to go about this is to clip the solder tabs, leaving enough of the tab to grab with small needle nose pliers. Then heat the solder joint and pull the tab. Use the solder wick to suck out the remaining solder. Adding a smear of rosin flux or flowing in a bit of fresh rosin filled solder can help with wicking out the old solder. It is important to not overheat the circuit board, hence the suggestion of flux or fresh solder.

    Solder wick, once filled with solder, stops working. I use the stuff that is about 1/8” wide and clip off about an inch after every use until the hole is clean.

    Then plug in the new batteries and solder them in place. If you have a newer board the batteries will have three tabs and a good replacement is Sanyo CR14250SE-FT. Also newer boards will have a “battery switch tab” that will disconnect the batteries if the cluster will be out of the car or the battery disconnected for a good bit of time, open up the cluster and move the tab to the disconnect position to keep from draining the battery.

    While you have the PCB out, reflow the solder where the fuel and temperature gauges mount. Also check with a magnifier for ant cracked solder joints and re-solder any yu find.

    If you don’t feel up to something like this, there are folks out there that will refurb the SI board pretty reasonably.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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