Results 1 to 22 of 22

Thread: Overheating Occasionally - solved, debris in heater core

  1. #1
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'

    Overheating Occasionally - solved, debris in heater core

    Hello all,

    Over the last few months my vehicle had been overheating seemingly at random. I've come to figure that it may be heater related.

    Car would start to get hot at the beginning of the driving day during longer and multiple red lights. On all but one occasion revving in neutral or accelerating would immediately drop the needle. The time it didn't, my heater was not getting hot and I had to pull over and bleed the cooling system which had amassed what seemed like gallons of air.

    I've come to discover that if I run the heater until hot at the beginning of my trip. I will have no issues during my drive even after I turn off the heater.

    I've checked:
    Aux fan comes on with ac on and dial set to full.
    Car would overheat with AC on or off.
    Water pump is new, metal impeller.
    Followed steps to properly and fully bleed system.
    No coolant leaks from hoses.
    Thermostat is new.

    And speaking of thermostats, I've noticed that they are rated for different temps. I thought that maybe I'd gotten the wrong one but the posts I've read don't lead me to believe it is behind the issue.

    I've also notced a musty smell coming from my vents when the AC is off but the air is on.

    Maybe the heater core has a leak and is causing air to enter the cooling system? (Also causing the musty smell)

    Or

    Maybe I have a gasket leak and I'm burning coolant in cylinder? (would explain intermittent 1221/1222 codes)

    Other than that the car is running great, even made another trip to Las Vegas with no issues. I've never had it overheat on the freeway either.

    Any suggestions are always greatly appreciated!

  2. #2
    Join Date
    Mar 2014
    Location
    Quezon City, Philippines
    Posts
    636
    My Cars
    '89 535i/5, '88 735i/5
    One thing you didn't mention is are you losing coolant? All your suspected causes would result in coolant loss.

  3. #3
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    Yes, do you have to refill coolant?
    T-stat different temp. versions do not matter, some open at 75, 80, 85, 90 degree C and so on, but once they are open they are all open

    "Car would start to get hot at the beginning of the driving day during longer and multiple red lights">>>>>this is a typical problem of the defective fan clutch, test it , write up by MWrench:
    Fan Clutch test
    First, lets discuss what the fan clutch does and why it is there. The fan clutch is just what the name says, it is a mechanism that will clutch the fan on and off depending on the need for more or less cooling air to flow thru the radiator. It is a thermostatically controlled device that when operating normally will vary the fan speed independently of the engine speed. When cruising down the road at freeway speeds, with outside temperature less then desert conditions, the fan should be merely be idling along, turning just fast enough to add a little air flow when needed, in this way the fan noise and drag on the engine is greatly reduced. When reducing speed, the fan clutch will sense higher temperatures thru the radiator and “clutch up” thereby increasing the fan speed to help maintain constant engine temperature. It may in fact, cycle as the temperature of the air thru the radiator changes depending on airflow. If the fan clutch operation is normal, when first starting the car, the fan clutch should “clutch up” and an increase in noise and airflow should be obvious. After about 60-90 seconds, the fan will un-clutch and the noise and airflow will drop. The fan will continue to turn but at a much reduced speed. As the engine warms and the thermostat opens to regulate the temperature, the air thru the radiator gets hotter and the clutch will sense this, thereby increasing the speed of the fan to maintain a normal operating temperature.
    First signs of trouble:
    A normal temperature indication at freeway speeds and an increasing temperature as the vehicle slows is one of the first indications of trouble. Many other things may give this indication but if the temperature seems to be stable at speeds but climbs in traffic or while stopped, this is a good indication that the fan clutch isn’t working correctly. As the temperature continues to climb, the auxiliary electric fan should start but may not provide enough air to keep the engine from overheating.
    Another sign of trouble is if the fan noise is high and never decreases after starting, and is there anytime the engine RPM is higher then idle, this means that the fan clutch is “frozen” and is not releasing. Although this will not result in immediately serious trouble, it will load the engine continually and gas MPG will be reduced. Load on the fan belt(s) will be higher and shorten the life of that component also.

    Testing the fan clutch:
    If you have reason to suspect that the fan clutch is defective, here is the recommended procedure to verify the condition of the fan clutch.
    1. Start the car (cold) with the hood open and note if the fan is turning, increase the engine RPM and note if the fan turns faster and the noise increases, if it does, first good indication, if it does not increase speed/noise, clutch is bad and needs to be replaced. (Remember, this must be tested after the car has been off for and extended period, over night etc.)
    2. Leave engine running and note if the fan starts to slow down after 2-5 minutes, speed/noise should diminish and even raising the RPM, the fan should not make as much noise as when first starting, if it does slow, this is the second good indication. If speed/noise does not decrease, clutch may be “frozen” and should be replaced.
    3. Leave the engine idle and watch the temperature indicator. When normal operating temperature has been reached, some increase in fan speed/noise should be noted, in particular when the RPM is increased. If temperature is fairly stable and the fan noise/speed increases or cycles, third good indication. If temperature indication continues to increase, with no increase in fan noise/speed, clutch is defective and should be replaced.
    4. After the engine is at normal operating temperature or above, is the only time that the “rolled up newspaper” test that many people talk about should be performed! Take some newspaper and roll it up into a long narrow tube. Be carefull, keep hands and fingers away from the fan while performing this test! With the engine at full operating temperature and idling, take the rolled up paper and insert it on the back side of the fan and try to reach the hub of the fan avoiding the blades until close to the hub. Push the rolled paper at the fan increasing the friction to the hub area of the fan. If the fan can not be stopped easily this is the fourth good indication, if it can be stopped the clutch is defective and should be replaced. Again, this test can only be performed when the engine is at or above full operating temperature.
    Testing can be performed in any order but just make sure the conditions during testing are those that are specified for that specific test.
    Do not continue to operate the engine if the temperature continues to rise and certainly stop if the temperature approaches “redline”.
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
    May 2017
    Location
    Sydney, Australia
    Posts
    15
    My Cars
    1992 BMW 735iL
    First thing to do is test your fan clutch as shogun mentioned above. That's the easiest to diagnose and replace (but not cheap if you go for brand new OEM).

  5. #5
    Join Date
    Jan 2016
    Location
    Ca
    Posts
    6,981
    My Cars
    2001 525it
    I remember these cars would have problems with the bleed hose from the coolant tank to the radiator, but I can remember if it was because they would get clogged or what.

  6. #6
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    good point, here the pics from Gale with the return hose http://www.nmia.com/~dgnrg/page_19.htm and here how the radiator cap works http://www.bimmerboard.com/members/r...nal/radcap.jpg
    M30 has a bleed screw, M70 not (only the oldest ones had), later that got modified to equalize pressures better in the system, instead of a bleed screw the M70 has a y-hose from the water pump to the radiator. http://bmwe32.masscom.net/sean750/V1...rMassMeter.jpg
    That Y-piece hose is quite expensive, you can DIY, easiest is with a Y-connector , take one made of steel http://userimg.teacup.com/userimg/88...bs/0000391.jpg
    plastic breaks http://userimg.teacup.com/userimg/88...bs/0000389.jpg http://userimg.teacup.com/userimg/88...bs/0000388.jpg

    But as per the description I put my money on the visco clutch.
    Shogun tricks and tips for the E32 series are HERE!

  7. #7
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    Thanks for the responses!

    Quote Originally Posted by cirrusblau View Post
    One thing you didn't mention is are you losing coolant? All your suspected causes would result in coolant loss.
    Hmm..... I've had the coolant level indicator come on maybe twice but this was more than a few months ago. I've been topping off the coolant when I bleed the system every few days. I'm not losing coolant in the traditional "puddle in the garage way" but I believe I am losing it somehow.

    Car overheated on my girlfriend this morning and got some good overflow action. Got to the car and saw a bunch of coolant in the street, expected a busted hose but everything.was intact. Fired up the car, opened the bleeder and watched the temp go down. Mainly air and coolant came out while the vehicle was running and only air came out with the engine off. Once again it was holding an abnormal amount of air, temp is good again for now.

    I am going to check out that visco fan tomorrow morning when it's cold again.

  8. #8
    Join Date
    Feb 2010
    Location
    Hampshire UK
    Posts
    8,867
    My Cars
    99 840ci Sport Indv
    Although for the V8's this is relevant for your problems:

    https://www.meeknet.co.uk/e31/BMW_M6...ing_System.htm
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  9. #9
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    Got up early today and did the fan clutch tests as directed above.

    #1 Pass: Fan speed did increase with throttle applied.

    #2 Fail: Fan did not slow after 2-5 mins

    #3 Fail: Fan stayed at it's previous speed even as the temp increased to operating temp and beyond.

    #4 Pass or Fail: The newspaper had no effect on the fan speed and I really tried to jam it in there. Not sure if that is a good or bad thing based on the outcome of the previous steps.

    If I understand correctly it seems like the fan clutch is frozen and cannot adjust speed to keep the radiator cool enough in the city.

    Please let me know what you think, thanks again!

  10. #10
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    May that are 2 faults. First a frozen visco clutch, but as the engine gets hot from time to time, also maybe a broken thermostat, which does not work properly or is jammed in a certain position.
    While the t-stats on E36 like my M3 usually stay in open position and the coolant never gots to operating temperature, on the E32 like my M70 I have seen many cases that when the t-stat breaks it get's too hot, here a pic of a broken t-stat from an M70 from one of my wrenching buddies.
    I would start with the t-stat, because if the visco clutch is really frozen, it would cool as much as it could.
    A 2rd cause just comes to my mind, but happens on the E32 less, that the water pump is broken, maybe you remember that there were some problems with older plastic pump impellers which came lose on the shaft, the shaft was rotating but the impeller not, causing heat problems.
    On M30 I so far have read one case where the metal impeller broke off the water pump shaft.
    I would start with checking/changing the t-stat.
    Attached Images Attached Images
    Shogun tricks and tips for the E32 series are HERE!

  11. #11
    Join Date
    Jul 2009
    Location
    Richmond, Virginia
    Posts
    1,683
    My Cars
    '88 735i, '06 RSX
    Perhaps you have a clog in your radiator, a small leak, etc. Of course, start with the cheap stuff first. New thermostat, new fan clutch, new water pump altogether might run you 120$ Behr radiator is about 150 USD new. If all else fails, it may be your headgasket going, which is not all that uncommon on the M30, could explain some of your coolant loss.

  12. #12
    Join Date
    Mar 2014
    Location
    Quezon City, Philippines
    Posts
    636
    My Cars
    '89 535i/5, '88 735i/5
    I think the visco fan is the least of your worries. From what you described, your cooling system is drawing air in which means you might have a small leak somewhere. When your engine cools down, the negative pressure on the cooling system will draw air in from where you're leaking. If your getting some strange smells from the vents chances are it's the heater core leaking.

  13. #13
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    I have been suspecting the thermostat but I did replace it only 3 months ago. Water pump is also new, and has the metal impeller.

    That heater core though.... My heater has been acting erratically lately. Earlier today my heater would not come on at all until I gave the engine some higher RPMs. The vehicle was already at operating temp at this time as well.

    I've read that the heater core can be slightly painful to service. Does the piping to the heater core fail or does the core itslef more likely to crack?

    Thanks for all the input as always!

  14. #14
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    it does not matter how old the parts are, check them, read this thread, with pic of cracked water pump impeller M30
    https://www.bimmerforums.com/forum/s...me-time-SOLVED

    Heater core usually/often the piping respect. the o-rings for the pipings, but in case that leaks, you smell it and you lose coolant http://www.bimmerboard.com/forums/posts/1074058/
    http://www.bimmerboard.com/forums/posts/1044927/
    http://www.bimmerboard.com/forums/posts/599811/
    Last edited by shogun; 11-07-2018 at 05:28 AM.
    Shogun tricks and tips for the E32 series are HERE!

  15. #15
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    I appreciate all the assistance! I just started working towards a degree in automotive technology at my local cc. A couple weeks back we finished tearing down, measuring, and rebuilding a Toyota V6. Last week the lecture was about cooling systems. Wow! Things are starting to really make sense now.

    From what I've read on the forums from others who've had similar issues I believe that the heater core is near the cause of this issue. Either it has cracked and is letting air in. Or some piping has done the same. But the quirk that always had me stumped was: Why does my vehicle cool down when I increase the rpms as the needle creeps towards the red? I'm fairly confident that because of the leak, my cooling system is not being pressurized properly at low RPMs, raising the RPMs temporarily raises the pressure and I get coolant circulating again.

    Again, this is what I think is happening, correct me if I'm way off please.

    For now I am going to bypass my heater core and see if my coolant loss persists.

    The advice is always appreciated!

  16. #16
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    When you increase the RPM, the belt driven water pump increases the speed too = circulation inside the cooling system is increased and that cools down the temperature again.
    The heater core has just the purpose to heat, but not the purpose to cool the engine coolant circle. For example when it is warm outside you have set the heating to zero = heater valves completely cosed and nothing goes thru the heater core.
    There are 2 cooling systems for your car, the small cycle just for the engine and the large cycle, for cooling the engine and heating.
    Copied from the M70 specification, you can use that also for the M30:
    The cooling system is a high volume design flowing symmetrically through both cylinder banks. The compact aluminum cross-flow radiator with a high ratio of fins and tubes has excellent heat exchanger qualities.
    Cooling system flow to the radiator is regulated with an 80 degree C thermostat. A ball type valve (arrow) in the thermostat plate allows air bubble bleeding following cooling system service.
    flow diagram:
    1. Radiator
    2. Return
    3. Feed
    4. Thermostat
    5. Water Pump
    6. Right Cylinder Head
    7. Left Cylinder Head
    8. Connecting Pipe
    9. Expansion Tank
    10. Heater Core
    11. Auxiliary Water Pump

    All accessory component rotary drive is accomplished with two poly-V type drive belts. Once correctly installed the belts are self-adjusting with automatic hydraulic tensioners (arrow) and thus are maintenance-free.
    Component Drive Distribution:
    Belt #1: Water pump, cooling fan and air conditioner compressor
    Belt #2: Alternator, hydraulic fluid pump

    see pages 12 + 13 http://bmwe32.masscom.net/sean750/M70info.pdf
    Shogun tricks and tips for the E32 series are HERE!

  17. #17
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    Hey all, hope you had a great Thanksgiving!

    I had some free time at work yesterday and a strong desire to see this heater core for myself. Got the cover off and found dried coolant on the inside and more dried coolant on one of the pipes.

    It looks like it could be a bad seal/gasket/O-ring. Could that be caused by a clogged heater core? And if so, what are my chances of unclogging it?

    I posted some pictures in my profile of the suspected leak area. If anyone has some time to check them out and give me a second opinion I'd greatly appreciate it!

  18. #18
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    For those which do not know how to see the pic: click on his name and then a new page opens and there you can see his profile pics.

    Accdg to the pic I assume it is a bad o-ring, the green-ish stuff on the core a bit lower is probably dried up coolant which dropped/sprayed down from the leaking area. I assume it is not a clogged heater core causing this, just the "usual" old, bad o-ring.
    Should be #18 64118377824 Gasket ring D=17.12MM BUT is says up to 06/1990, so better double check with the VIN http://www.realoem.com/bmw/enUS/show...diagId=64_1810

    Behr heater core original BMW 64118372523 is quite expensive, almost $300
    Shogun tricks and tips for the E32 series are HERE!

  19. #19
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    Accidentally deleted my last post trying to edit it.

    I found two of those odd rubber bits actually. One in the first pipe and one in the third which makes me think they may orginally been part of this heater core. I also asked my auto shop professor and he seems to think it may be a home made gasket that found its way into the cooling system eventually becoming trapped in the heater core, although he is admittely not very familiar with BMW heater cores.

    Either way the probably be should not be free floating in the heater core.


  20. #20
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    Good that you found it. I can only guess what it is: maybe a part of grommet #16 http://www.realoem.com/bmw/enUS/show...diagId=64_1810
    looks like this https://www.ecstuning.com/b-genuine-...t/64118390864/
    could be that someone before was working on the heater core pipes and pushed the pipes too hard into the grommets without seeing it and cut part of the grommet and it slipped into the pipe and then into the core.
    Shogun tricks and tips for the E32 series are HERE!

  21. #21
    Join Date
    Apr 2017
    Location
    San Diego, CA
    Posts
    232
    My Cars
    90' 735iL, 90' 535i, 93'
    Just a quick update. Problem solved, debris in heater core.

    I've had the car stress tested multiple times including the ultimate stress test a vehicle could endure... The In N Out drive thru.

    No more overheating! This had been doggin me for months and I can drive with ease of mind again including another trip across the desert to Las Vegas.

    I greatly appreciate all the assistance from the forum!

    Now to figure out that CEL 1221(2).....

  22. #22
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    code 1221 and 1222 I explained here http://www.bimmerboard.com/forums/posts/669551
    Shogun tricks and tips for the E32 series are HERE!

Similar Threads

  1. 95 740iL overheating after heater core swap
    By dvine1 in forum 1995 - 2001 (E38)
    Replies: 16
    Last Post: 09-30-2015, 08:50 PM
  2. Replies: 8
    Last Post: 08-20-2012, 02:21 PM
  3. Heater core
    By QuestMCoupe in forum 1991 - 1999 (E36)
    Replies: 8
    Last Post: 11-28-2002, 11:30 AM
  4. Heater core ........
    By Dade in forum 1995 - 2001 (E38)
    Replies: 3
    Last Post: 10-26-2002, 04:46 PM
  5. Heater core replacement
    By Robcast in forum 1991 - 1999 (E36)
    Replies: 5
    Last Post: 02-04-2002, 07:36 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •