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Thread: 1990 735i overheat issue

  1. #1
    Join Date
    Jul 2016
    Location
    main street
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    8
    My Cars
    1999 m3 vert

    1990 735i overheat issue

    My e32 suddenly started overheating for no reason I could figure out.

    I replaced the water pump, the fan clutch, thermostat, flushed and changed coolant.

    car seemed to work fine, I took it on a road trip and every once in a while when accelerating hard I would smell burning rubber, but I thought nothing of it.

    after 300 miles going up mountains and stuff with no overheating issues, I accelerated really hard to merge onto a freeway and the car started overheating badly again. and I smelled burning rubber again badly

    belts are all tight.

    I don't understand why I smell burning rubber, I don't know if the harmonic balancer has rubber on these cars ?

    I drove it again the next day, no overheat issue, so ?

    any ideas ?

    thanks

  2. #2
    Join Date
    Jun 2011
    Location
    NYC & Long Island & So FL
    Posts
    1,119
    My Cars
    '93 740il '84 633Csi
    Get an infrared thermometer and see what is hottest. Have you looked at plug boots and any hoses that may be too close to the exhaust manifold. Has your antifreeze level been stable? When you flushed the block, was there any crud buildup?

    Don't assume that a new thermostat is good. You can test it on your stove with a candy thermometer and run it through several cycles. What brand did you install?

    Sent from my SM-G955U using Tapatalk
    Last edited by Sansouci; 09-17-2022 at 08:32 AM.

  3. #3
    Join Date
    Jan 2005
    Location
    Japan
    Posts
    54,654
    My Cars
    11/88 E32 750iL+98 E36M3
    is the return hose clean? See here http://www.nmia.com/~dgnrg/page_19.htm
    Shogun tricks and tips for the E32 series are HERE!

  4. #4
    Join Date
    Oct 2008
    Location
    Romania
    Posts
    110
    My Cars
    1994 BMW E32 730i M30
    Billmr, I believe it is complicated to remotely diagnose your problem, based on the information provided. The small of burning rubber is quite puzzling.

    If the engine did not ever overheat before the cooling system service, and started to overheat immediately after that, I would say that you should investigate the quality of the new parts, and if they were correctly installed.
    Start the easy way. As Sansouci suggested above, test the thermostat. Then properly bleed the cooling system, and check again for overheating.

    If it still happens, then you may even suspect a blown cylinder head gasket, and run some tests to diagnose it.

    Please keep us updated.
    --
    1994 E32 730i M30 manual
    ex- 2006 E86 Z4M Coupe
    ex- 1986 E28 535i

  5. #5
    Join Date
    Nov 2007
    Location
    SF, bay area
    Posts
    251
    My Cars
    94 740, 74 wagoneer
    Burning rubber smell could be oil being cooked on the exhaust...

    As for the overheating, make sure that your expansion tank cap is seated and is in good shape, no cracks on the rubber seals, a lack of pressure will increase your temp reading

  6. #6
    Join Date
    Aug 2009
    Location
    Houston,Texas
    Posts
    265
    My Cars
    83 533 92 325 97 m3
    I like to pull the spark plugs and look at them then I pressure up the cooling system and keep checking it and let it sit overnight and check for coolant in the cylinders.

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