1991 BMW 750il wont start! Mechanic stuck! Been in shop >8 months!

[whiskychaser]

found it in the component location index, X15 connector 30 pins, location below left side of dash on LH side of connector bracket, see 7100-25-2 http://shark.armchair.mb.ca/~dave/BMW/e32/e32_91.pdf

Many thanks. Found what I was looking for on page 0671-06. Live circuit goes Fuse 10 -> X206 -> X15 (pin 7) -> X577.
X577 feeds the chime, OBC and park vent. So as above, I would be looking for a short to ground at X15 (pin 7) and then work forward to X577 and ultimately, the items it feeds.

[Bimmerboatmd25]

Well I have another positive update! Thanks for the advice whiskychaser! Your intuition about pin 7 was correct. I de-pinned pin 7 from the X15 connector, insulated it, and plugged X15 back in. It fired right up!

I checked the coolant level before driving it and it was low so topped it off before I left. It appears there is a small crack in the radiator so I will be ordering a new one tonight. What radiator do most install that is best? I could not remember if Nissens is what BMW originally used. Im already on my second - but cant justify spending $800 on an all aluminum one . Any advice on that front is appreciated. Also advice on where to find new radiator hoses? I also was wondering if I should replace the expansion tank at the same time I don't think I've ever replaced since I've had it. The water pump and the thermostat and housing have already been done. Was thinking about putting in an aluminum housing if someone can point me in the right direction to buy one.

I was not able to drive the car far with the radiator cracked but did take it around the block a few times! Yahoo! No more limp mode, making good power, and transmission shifts smoothly so appeared to dodge a bullet there for right now.

Now on to other new issues . It looks like the rear self leveling shocks are not working right now - a bit disappointing as I paid a shop about $2k to fix a cpl years ago. Cant remember what all was done at that time but going to call the shop in the morning and get the invoice.

The brakes didn't appear to function properly -when you push the brake pedal slowly and firmly it acts normal but if you stab it quickly, it gets very hard for a moment , then starts to go down like a normal pedal. Is this the pressure accumulator? It appears no one has that part anymore - finally found one place that does have only 1 but it costs $300.

Tomorrow I will try to pin point root cause of the short and try to see problem with rear self leveling shocks.

Again thanks for all the help! This car wouldn't have a chance to stay on the road without it!

[shogun]

It does not matter that much which brand nowadays, the Hella/Behr are also no longer produced in Germany but come from South Africa and the cheapo version from them is made in China https://www.bimmerforums.com/forum/s...ative-Products
Most radiators start leaking or break when the engine mounts are no longer good and the engine moves much more clockwise/anticlockwise and the radiator is fixed on the chassis, so that makes stress to the parts.
Nissens is o.k., but also some others no name, check - if you want to get a cheap one - at rockaurto.

What is the actual problem with the SLS? Maybe just an adjustment of the level is necessary and the lever on the rear axle, see my website.

"The brakes didn't appear to function properly -when you push the brake pedal slowly and firmly it acts normal but if you stab it quickly, it gets very hard for a moment , then starts to go down like a normal pedal. Is this the pressure accumulator? It appears no one has that part anymore - finally found one place that does have only 1 but it costs $300. "
panic stop>>> https://www.bimmerforums.com/forum/s...ebi+brake+bomb
Get a cheap one from Febi and modify the connections https://www.bimmerforums.com/forum/s...ebi+brake+bomb

https://www.bimmerforums.com/forum/s...n-to-E31-style

[Bimmerboatmd25]

Don't want to put anything in cheap for the cooling system. Planning on driving this car and want to feel comfortable taking it on a long trip every now and again. But I've spent a lot already as you know. Not seeing much out there other than Nissens. A cpl cheaper brands I'm not familiar with. No genuine bmw anymore I guess.

The problem with the SLS is that it doesn't appear to be working . The front of the car sits much higher than the back. I will take a look at your website again and see if that is the issue.

I read through the link you gave on the accumulator. Very interesting. So since my car is a 1991 it has two connections right? So i would buy a febi for the e23 at 30 bar pressure and send to a hydraulic shop to change the connections? Was not able to see the photos for some reason. Really appreciate the help and that would be big saver. Just making sure I am understanding correctly. It also sounds like they haven't made these for awhile and only have a shelf life of 5 yrs? So the one I found for sale is probably old. The only reason it is still there probably is bc it is will call only (local pickup) . It is in Los Angeles though, which lucky for me is where my dad lives and he could pick up for me.

Didn't see the last link you posted. Saw some photos and making more sense on what needs to change now.

[Bimmerboatmd25]

Shogun how do I check if my engine mounts are bad? I haven't noticed excessive shakiness while driving or accelerating. One of the reasons I've always loved the car is how smooth it is to drive. How hard/expensive are these to replace. So basically what you are saying is that if the cause of the cracked radiator is from bad motor mounts - it is likely the new radiator will have the same issue and crack again relatively soon?

[shogun]

It depends, maybe it is just age, normally if the shock mounts are bad, then the damage is often in this area in my opinion, also caused by old, hardened heater hoses http://bmwe32.masscom.net/sean750/ra...eplacement.htm
but of course it also depends on the age of the radiator. For example my 750 rad has been replaced in 30 years 1 x only.

Difficult to see if an engine mount is dead, here some info from Gale http://www.nmia.com/~dgnrg/page_10.htm
You can only really compare new and old one side by side, like here where I posted a pic, see the height difference http://produkte.bilder-speicher.de/1...t-und-neu.html

Do that repair later, in any case if the motor mounts have never beem changed, it is time to do so.

Before you buy a new brake bomb, check which version you have, 1 or 2 connections. Also this is not urgent, the brake will still work.
SLS: the front always looks higher even on my car, because the shape of the front fender is different. You can adjust the rear by changing the lever position. Also this is at the moment cosmetics, first fix the serious things.
Shelf live 5 years: that is based on ATE internal stock regulations = 5 years, the rear bombs last much longer. Many have still the ones from original built year installed.
Inspect the one you can see, normally the production date is stamped on the housing.
Also my brake bomb is from 1988 and still works fine.
a bad accummulator is shown here by Gert, he can stick in a long metal http://www.bimmerboard.com/forums/posts/1261417/

Edit: checked prices a bit at rockauto for 1991 750iL
radiators 85 - 150 $ , Nissens $150
radiator cap (always use a new one, some radiator sellers even insist on that) $7.50
motor mount brand anchor $52
in case you want brand names, check with FCP, they have lifetime warranty

[Bimmerboatmd25]

Thanks for all the info Shogun . Extremely helpful as always! I just went ahead and bit the bullet and ordered the aluminum Zionsville radiator . The tipping point for me was reading through the forums where ppl had to replace their new nissens after about 12 months . I know the Zionsville is probably overpriced but for peace of mind knowing I won’t have to replace it again ide say it’s probably worth it . The other issue is what if I am on a trip and it happens or if my fiancé is driving - doesn’t pay attention to the temp gauge and permently damages the engine. I also ordered the brake bomb and had my dad pick it up. Mine is the one with 2 connections. Apparently you cant fly with these or it damages the part due to the gas in it? Regardless having it now shipped using UPS ground to Dallas. Hopefully arrives in a few days . They said it would take about ten days to get the Zionsville radiator built so that gives me some time to sort these other issues out now. Will spend some time on the car next week looking for the short off pin 7 and hopefully install new brake bomb by then. What motor mounts do you recommend shogun? Was thinking the motor mounts probably aren’t something you want to use aftermarket parts on. I’ve been having a hard time finding all new radiator hoses - do you know where these can be bought? Thanks again for all the help and advice

[shogun]

check https://www.fcpeuro.com/ they have lifetime replacement.
cooling hoses genuine https://www.fcpeuro.com/BMW-parts/75...=5&b=5&d=71&v=
BMW Engine Mount Kit - 22116750820KT Part #: KIT-22116750820KT made by Corteco should be o.k. $111.86
also get trans mounts in case never changed before http://bmwfans.info/parts-catalog/E3...box_suspension
center mount/bearing o.k.? #1 http://bmwfans.info/parts-catalog/E3...onst_vel_joint
in case you cannot find the parts there, Pelicanparts, ECS, autoausaz and some others are good sources https://www.bimmerforums.com/vendors-2/

[Bimmerboatmd25]

Thanks again for all this. Just finished ordering all new radiator hoses from fcp, engine mount kit, trans mounts, center mount/bearing, and genuine bmw expansion tank. I've got my worked cut out for me but really think most of the issues have been dealt with after this and should last for many years to come. Any other things I should think about replacing while I am doing an overhaul ? Car has 160k miles if I have not already specified

[kce1900]

Car has 160k miles if I have not already specified

Are you going to be ready to add 2k miles in May? Have a look at this thread: The Vintage 2019. Wouldn't it be amazing if you could join us there after all the xxxx you went though? Here's a picture from last year: click. Either way, keep going.

[shogun]

Any other things I should think about replacing while I am doing an overhaul ? Car has 160k miles if I have not already specified

well, if you want, we can add more

there is always something on our old cars which needs to be checked, repaired, improved. Simple list in order of importance:
Condition of fuel hoses in engine bay
System voltage is at least 12.8V
Condition of heavy electrical cable from alternator to charge terminal
Condition of vacuum hoses to fuel pressure regulators
Condition of fuel vapor hoses from charcoal cannister to DKs
Presence of lipping on brake discs
Condition of flexible brake hoses
Condition of tires
Cracks/leaks in radiator at gearbox cooler connections
Leaks from water pump
Excessive play in water pump bearings
Condition of water hoses and heater water valves
Condition of battery - presence of sulphates on terminals - cable condition
Condition of steering linkages - damage to boots - loose joints - bent linkages
Excessive play in steering
Cracks in/leaks from sump
Leaks from oil filter hoses/connectors


See my website under check list. There I also have the official inspection I and inspection II checklists. But I would suggest, first drive and enjoy.

[Bimmerboatmd25]

kce1900 that looks pretty cool and would be a fun trip! Will let you know how things go and if she is ready. Having some difficulties replacing some of the new parts.

Motor Mounts are done.

Transmission mounts are not done - How do I access these without removing the exhaust? Exhaust is completely rusted out and looks like it will crumble if touched. I have little confidence the header exhaust flanges will come apart intact. Dont want to break any of the studs. Any advice is appreciated on this front as well. Or if there is a better way to do this.

Rear sway bar got ripped out of the mount bracket on the left side and is bent . Hoping I can repair this and get back together

Brake Bomb - Not done - The fittings on the brake bomb are seized and I was unable to get enough leverage to remove. Access is very poor. Any advice on best way for doing this is appreciated .

All of the rear suspension bushings appear to be completely shot . The two dogbone pieces are super dead and just flop around . Any advice on where to pick these parts up reasonably is appreciated.

On the rear self leveling suspension wondering if the problem is the original rear accumulator.

Thanks again for any input!

[Bimmerboatmd25]

Looks like Turner Motorsports sells most the rear suspension bushings I need. I guess I should replace with aftermarket poly bushings?

- - - Updated - - -

Also FYI Turner Motorsports has a decent deal on complete plug wire sets for both sides with new bremi connectors for $327 all in. I know I paid more for the set I have on now. Here is the link https://www.turnermotorsport.com/p-3...csi-e32-750il/

[shogun]

I would stay with OEM rubber bushings. My thinking is that bushes are meant to flex and to reduce the transfer of vibrations. Ask yourself "What would happen if you welded the diff to the crossmember?" This is effectively what you do if the bush is too hard. Hard bushes are good if the body they are mounted to is strong enough to take it. They are also o.k. for bushes that are only used to support a twisting rod.

some comments from users:
it makes the steering feel a lot sharper with the poly bushes I certainly noticed the difference going back to standard oem again. But for everyday use I'd say oem are a much better option for the front.

I fitted powerflex bushes front and rear to my E36,they made the handling much sharper than the worn oem items but made the ride harsh and crashy on typical roads.
On my E46 I fitted oem but used genuine M3 at the rear and the ride and handling is like a new car,the M3 bushes are a straight swap on a 328Ci and are reputed to last a lot longer.

I tried every bush going, even machined my own housings so i could try some M3 ones (they are a smaller diameter and need an "adaptor" to the wishbone "hex") and in the end, i think the std OEM ones are the best all round compromise, funny that, BMW must know a thing or two about ride and handling. As mentioned, most people replace knackered OEM ones with polybush or equivalent and then praise the improvement. TBH, the state mine came out in after 55k, replacing them with a pair of dead mice would have been a similar improvement

Poly bushes are definately the way to go and fitting OEM bushes is only a quick fix so be ready to replace then again soon.The poly bushes only feel harsh because you are replacing very soggy, worn out rubber bushes. Replacing them with the poly will inprove the steering response and feel and even sharpen up the braking.The poly bushes are designed to make minimal difference to ride noise and comfort and I would never go back to those soggy, expensive, fast wearing OEM bushes again

And for the rest of us, who just drive around normally, the OEM bushes are the ones to have ;-) Ask youself why BMW would put a compliance bush in a location that has no benefit?? Answer, they wouldn't.........

I agree that powerflex give slight gains in handling but in my experience I really don't think the longevity of the front bushings are any better than that of the standard OEM. There simply not tight enough on the wishbone or at least the powerflex ones don't seem to be.

considering that i have spent the last 20 years of my life, designing and developing cars for just about every worldwide manufacturer, i can truthfully say, no, we don't build in deliberate life limiting. yes, we might have a compromise on durability vs functionality where the benifit to the customer is significant enough to outweight the negative(in this case much better lateral ridge bump absorption). (and OEM's take parts failure inside or outside warranty period very seriously these day). All the parts that are fitted to your car WILL have passed the manufaturers durability targets. take the longitudinal compliance bushes as an example. if driven hard, they wear after approx 50-60k miles (most owners will get over 100kmiles before they notice the difference, but PH'ers tend to drive harder etc).

[Bimmerboatmd25]

Really really good info here Shogun. Extremely helpful. Sounds like OEM is the way to go as usual. Good for me too bc they are cheaper than a lot of the poly bushings.

I am tempted to replace the exhaust on my car as it is super rusted. Has anyone done this before? I looked online and saw billy boat makes an exhaust for our car but not sure I want to go with something so far away from stock. Always the chance I don't like it and I don't want to take away from what the car is. It appears the billy boat exhaust connects to stock cats and then to the h pipe behind manifolds. Link here https://xlr8performance.com/i-11208-...fbmw-0420.html . Or is it better to just go to a local exhaust shop and have something made - thinking this might be the cheaper route. Do our cars tend to run into problem with the cats ? Just curious when I should expect to need to replace these and if it is a common problem on higher mileage vehicles like mine

I also ordered new stainless brake lines today from FCP EURO to replace original soft lines ... seemed like a good deal.... link here https://www.fcpeuro.com/products/bmw...steel-bmw-1200

Still waiting on aluminum radiator from zionsville. I placed order on the 1st this month... they said about ten days ... when I called on Monday for an update they acted like I never even placed the order and said would call me back next day with an update.... still waiting on call back. I know these guys are enthusiasts too so I'm not that concerned but hope they. get it shipped out soon.

Goal is to have the car back on the road by the end of the month!

[shogun]

as for exhaust it depends what you want, I personally consider the E32 750iL as a (former) upper class limo and do not like to have a loud exhaust.
The original exhaust as well as the cats last very long, and the original cats are of high value for the scrap dealers and catalytic converters are popular among scrap-metal thieves. The aftermarket ones are much less in value. Catalytic converters contain platinum, rhodium, and palladium. The metals are expensive, and thieves sell the converters to scrap yards for $... per piece, depending on the size of the converter and the current rate on the metals inside it.
Tell us what you want and someone will chime in who has done it. Maybe cheapest is to go to a local shop to have something made.

[Bimmerboatmd25]

I agree with you Shogun. I actually have always loved the way the stock exhaust sounds and like you said its basically a luxury limo not a sports car. I understand stock cats are very expensive and makes sense with all those expensive metals in it.

I will try to take some photos of the underside and post tomorrow.

.... Now on a completely different subject I think I remember you posting a video somewhere of an E32 750il accelerating on the autobahn to top speed with one of your chips - I believe hitting 180mph or 290kmh? Ive gotten into a bit of a debate with a friend on top speed of our cars and was trying to track that video down . He did not believe e32 could hit 180mph with its weight and drag - was hoping to prove him wrong without having to test it out in my car in the states lol

[shogun]

180 mph is 290 kmh, that is tough/impossible to reach for the E32 750, the shape of the car is not that good for top speed. Maybe on the cluster, but not by GPS.
https://www.youtube.com/watch?v=fju3oKPYfCU
But here is a normal 750iL https://www.youtube.com/watch?v=4wU2yWtc-VM
https://www.youtube.com/watch?v=eC15TA58q2s
The EURO 750 has a limiter at 250 kmh, so if the limiter is out, maybe on the cluster depending on engine condition shows as top speed 260-280kmh. The E32 Alpina B12 has 350HP and in the Alpina brochure is mentioned as top speed > 275kmh

It also depends on the final drive as we discussed here https://www.bimmerforums.com/forum/s...-E32-Top-Speed

[Bimmerboatmd25]

Thats pretty insane top speed for a car this old, amount of hp, weight, and drag. I couldn't remember what top speed was once the 155mph speed limiter is out. But now I do! Thanks for the videos and refresher. My favorite one was the last video with the two guys with giant smiles haha! That would be me no doubt! Turns out my buddy was spot on his guess was 160mph but I thought ide read somewhere they could go a bit faster with the limiter out. My car has the 3.15 LSD I believe. I have heard of upgrading to 3.91 LSD out of like an M5 but I love the way it drives now so why change and I guess a compromise with top speed. HAHA I guess I need a radar gun detector and road trip towards El Paso tx to test it out myself

[Bimmerboatmd25]

IMG_0947.JPGlooking forward to cleaning her up again and finishing last details after getting everything mechanically as it should be. Last thing to take care of will be droopy headliner and interior.

[Bimmerboatmd25]

Shogun - wanted your opinion on the original fuel pumps. They are both original to the car - I've replaced most of the fuel system already and was wondering if I should just go ahead and replace them preventively since they are 28 yrs old. I also haven't done anything with the fuel injectors. Also, the valve lifters are original idk if and when you recommend replacing these? I was also wondering what oil you recommend running on car with higher miles? Ive heard of going to a heavier weight oil which I have not done.

[Bimmerboatmd25]

One other thing I should probably mention is that when Frank was doing all that engine work - he found that one of the head bolts were snapped and the bottom half of the bolt was stuck in the block. I decided not to worry about it right now since no sign of head gasket failure and since there are 12 bolts I figured could go a really long time without any issue. Am I correct in believing this can only be fixed by pulling the engine and many hours labor? I figured once it gave problems I would pull the engine, do head gaskets and a bunch of other stuff as well as making the engine look aesthetically new again. Let me know if this is flawed mindset and I should just do it now, I really don't want to wait much longer to drive the car . As said before I was thinking I will be back on the road come April 1st if I don't tackle this problem as well.

[shogun]

My original Bosch pumps died with age 28, suddenly from one day to next one pump was dead. http://www.bimmerboard.com/forums/posts/1264535/
Replaced both pumps (not the cpl. unit) and then I noticed finally how weak they already were after so many years, when I tested the new pumps after installation, I used a wire from B+ post to fuse 23 for bank 1 and then fuse 24, just touching on top of the fuse for 1-3 seconds with ignition off, then one can hear the fuel pumps running and the fuel hoses get hard, then I noticed some leaks on the fuel hose connections in the engine bay, which were not there with the old pumps = they became weaker.
Bosch details from repair book: operating pressure is 3 bar, conveying capacity at 12 V 1.7 liter/minute , capacity against counterpressure 875 cc/30 seconds, power consumption 5.5A
If you want to go cheap, E36 fuel pumps also fit. Autohausaz has the M70 fuel pumps from Bosch on sale, Bosch Fuel Pump, Electric P/N: 69493 Bosch Cross References: W0133-1923365, 61310, GFP316, 0580453010, 16141179710, 16146768653, BMW 750iL, 850i, 850Ci, 850CSi for $ 116, also change the fuel filters and the short rubber hoses in front and aft the filter above rear axle. Filter only cost abt. 10-14 $ each.
And while you are in there also both fuel pressure regulators and the vacuum hoses for these.
Fuel injector you can aks a shop like Mr.injector for reman, that you can do when you make the top end overhaul, see my website. Valve lifters you will notice when they make noise.

Engine oil: my old autodata CD says with regards to engine oil: engine code 50 12A (M70 engine): cold climate SAE 5W30, moderate climate 10W40, hot climate 15W40, Engine oil classification: API/ACEA SH/A2-96
engine oil - alternative - moderate climate SAE 10W60 Synthetic, engine oil - alternative - moderate climate API/ACEA SH/A3-96
Volume: Engine with filter: 7.5 litres, M70 engine, Japan version M70 engine: 8.25 litres with filter (because of larger engine oil cooler)

I drive all year round 10W40 = moderate climate. Before I always used 20W50, but more difficult to get nowadays.

One other thing I should probably mention is that when Frank was doing all that engine work - he found that one of the head bolts were snapped and the bottom half of the bolt was stuck in the block. I decided not to worry about it right now since no sign of head gasket failure and since there are 12 bolts I figured could go a really long time without any issue. Am I correct in believing this can only be fixed by pulling the engine and many hours labor? I figured once it gave problems I would pull the engine, do head gaskets and a bunch of other stuff as well as making the engine look aesthetically new again. Let me know if this is flawed mindset and I should just do it now, I really don't want to wait much longer to drive the car . As said before I was thinking I will be back on the road come April 1st if I don't tackle this problem as well.

Maybe you ask an engine specialist, it might be possible to get the bolt out w/o the engine removed, have read a long time ago on some other forum (forgot where) that it is somehow possible to remove the heads without engine removed.
But a broken head bolt can become dangerous when coolant enters the oil or oil enters the coolant!

[Bimmerboatmd25]

Thanks for all this - helps a ton. Going to go ahead and replace both fuel pumps - seems to only make sense after all the work done. I will order from Autohausaz - thats a really good deal - the ones I was looking at were more like 150 each. Ive already just in the last year replaced both fuel filters and the short rubber hoses you mentioned. I assume that I can just do the fuel pumps then. Im going to use 10w40 you mentioned going forward unless I can locate some 20w50 - I live in north Texas and would consider our climate moderate - we do get some cold weather in the winter occasionally. Ive already bought two new Bosch fuel pressure regulators just haven't installed them yet. Ill do this at the same time I do the fuel pumps. Where can I find the vacuum hoses for these? For some reason had a tough time locating these - I know I must have just missed it and they have to have on the web.

[shogun]

use realoem.com and search with your VIN and you find 11727545323 Vacuum hose 3,5X1,8mm http://www.realoem.com/bmw/enUS/show...diagId=13_1387
any car accessory shop has these or you can also use silicone or fuel line hoses of this inner dia. 3.5mm hose.