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Thread: Slightly Right of Center Temperature Gauge

  1. #1
    Join Date
    Feb 2018
    Location
    Bay Area
    Posts
    65
    My Cars
    1993 Calypso e31 850ci

    Slightly Right of Center Temperature Gauge

    I just finished a cooling system refresh after the car overheated slightly at idle. Found out that the lower hose from the thermostat housing (part #11531711002) was busted and decided it was was time to buy a new fan clutch, radiator, water pump, thermostat, thermostat cover, and all hoses.

    IMG_6182.JPG

    After install, coolant flush and bleed, my temp gauge is slightly off center. It was like this previously, but I chalked it up to the fan clutch being worn. But this is a brand new fan clutch. THIS THREAD suggests it's the thermostat itself, but I just popped in a new one with the system refresh. I did a bit more digging and came across THIS THREAD, but I'm not sure if my reading comprehension is low, but I might be looking at replacing the temperature sensor? If so, there's two on top of the thermostat housing and I'm unsure which one.

    Is this a matter of me just needing to bleed and burping the system again? Is this a normal occurrence and I'm just obsessing over a small thing? An image of my gauge is below:

    IMG_6244.JPG

    Also, in going through this repair, I wondered why the hell BMW did not use a gasket between the thermostat housing and thermostat cover. I am extremely paranoid the aluminum cover will warp and fail over time. According to RealOEM and other diagrams, the o-ring goes outside of the thermostat, and then the cover. I've included the diagram for reference. Anyone else have this concern or is it just me be an ass?



  2. #2
    Join Date
    Nov 2009
    Location
    Realville
    Posts
    1,216
    My Cars
    93 525iT,91 318i
    Maybe you just worry too much? The O-ring seal is the gasket, it's just made from a superior material using superior engineering application. If it was a bad idea, BMW and many, many other manufacturers would have stopped doing it that way.

    Regarding your temp gauge, you said you installed a new thermostat. Those things are mechanical devices and have a +/- tolerance for keeping a set temperature. (Curious if you bought an OEM t'stat or aftermarket). Same goes for the temp sensor; it measures with a +/- error. If it was exact, it would have actual numbers on the gauge face. Replacing the sensor may change the position of the needle, but it will not change the temperature of the coolant. It will still be the same regardless of what new position the needle settles on. I suggest you relax and enjoy the car for a while and just monitor the gauge. If it meanders around or starts heading off over time in the red direction, you may still have an issue.

  3. #3
    Join Date
    Feb 2013
    Location
    Burlington, Ontario
    Posts
    1,122
    My Cars
    1991 750iL+ 2008 535xit6
    My 540 has always been slightly right-of-centre. It did 280k kms on the original engine, nary a problem.

  4. #4
    Join Date
    Jul 2016
    Location
    Seattle, WA
    Posts
    90
    My Cars
    2004 R32, 2011 A4 Avant
    I believe you can pull up the coolant temp the sending unit is reading on your MFD.

    As had been discussed many times before, the temp gauge on the e34 has a deadband. This means it will point to (or near) center for a large range of actual engine coolant temperatures. There are multiple posts which link BMW documentation that describes this ‘feature’. Should be able to find it pretty easily via search.

    If I were you, I’d figure out how to get the actual sensor temp displayed on your mfd, then compare that to the BMW documentation on the gauge function. That should easily tell you if the engine is really running on the high side of ‘normal’ or if your dash gauge is messed up.


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  5. #5
    Join Date
    Oct 2018
    Location
    Birmingham
    Posts
    130
    My Cars
    E34 525 1990 5HP18
    From the looks of it, this is normal for your engine/temp sensor wiring/current temp senderr/dash temp gauge. Your fan clutch sually spins freely - driving on the highway is enough to cool the engine down and if the clutch locks up it is unnecessary load on the system. So the readings before and after the clutch fan change may well be the same.

    Your engine coolant temp sensor should be blue tipped. The temp sender should be brown tipped.

  6. #6
    Join Date
    Sep 2006
    Location
    NW suburban Chicago
    Posts
    16,302
    My Cars
    hiss by my window
    Variations between cars of a needle's width or so are pretty common and nothing to worry about. I've had them both ways of center and never an issue. I assume it is manufacturing tolerances/age of the temp sender and perhaps the gauge too.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

  7. #7
    Join Date
    Feb 2018
    Location
    Bay Area
    Posts
    65
    My Cars
    1993 Calypso e31 850ci
    Quote Originally Posted by locknload View Post
    Maybe you just worry too much? The O-ring seal is the gasket, it's just made from a superior material using superior engineering application. If it was a bad idea, BMW and many, many other manufacturers would have stopped doing it that way.

    Regarding your temp gauge, you said you installed a new thermostat. Those things are mechanical devices and have a +/- tolerance for keeping a set temperature. (Curious if you bought an OEM t'stat or aftermarket). Same goes for the temp sensor; it measures with a +/- error. If it was exact, it would have actual numbers on the gauge face. Replacing the sensor may change the position of the needle, but it will not change the temperature of the coolant. It will still be the same regardless of what new position the needle settles on. I suggest you relax and enjoy the car for a while and just monitor the gauge. If it meanders around or starts heading off over time in the red direction, you may still have an issue.
    Gotcha. Thanks for the explanation. I def worry more about this car than my previous cars, but it's so sexy, it's worth the preventative measures. I have a gut feeling that a head gasket job might be on the table within the next 2-3 years. I'm waiting for the day I replace my spark plugs and see coolant related corrosion, or my coolant levels dropping over time and there's no sign of a leak.

  8. #8
    Join Date
    Apr 2014
    Location
    Northern VA
    Posts
    184
    My Cars
    e34 m5, touring; e46 (x2
    As a quick and easy check, you may want to make sure that your connectors for the coolant temp (blue) and for the coolant gauge (brown) are not crossed. On my '95 e34T (m50), I had the same needle gauge reading as you are experiencing, which was due to the connectors being crossed. Once my sensors connectors were swapped, my coolant gauge now reads slightly below half-way. May not be your situation, just trying to be helpful...

  9. #9
    Join Date
    May 2004
    Location
    Billings, MT
    Posts
    6,720
    My Cars
    2013 328i xDrive
    According to BMW anywhere between the left line and right line is normal operation temperature. Keep in mind you sit a little to the left of the gauge when you drive. I think if you lean over and look at the gauge dead on it'll probably be exactly in the center. I don't see anything to worry about based on your picture. And as others stated, that o-ring is the seal for the cover, so no gasket is necessary.
    -Chris
    My e30 build thread/color change here

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