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Thread: E21 M10 running real hot..help?

  1. #1
    Join Date
    Jan 2012
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    Default E21 M10 running real hot..help?

    I have an '81 320i with the stock m10 in it. My thermostat decided to stop working one day on my way home. My temp gauge hit about 85% so I stopped and let it cool down for a solid two hours before turning it back on. I realized the thermostat was not opening up so I swapped it out..that kept me from overheating but my engine still runs at about 70/75 percent on the gauge.

    The first time my aux fan did kick in and just stayed on the whole time until i pulled the fuse. I later on put the fuse back in and now it doesn't ever turn on.

    Water pump replacement next?

    If you're familiar with the m10..the top two hoses that run into the thermostat and radiator get unbearably hot while the bottom hose running from the radiator into the thermostat stays completely cool. I know that the lower hose should be coolest but at times it feels as if there isn't even any water running through it?

    I haven't had much time to work on it because of school and it is my daily so commuting has been real hard which is making me lean towards taking it to a shop but I don't know of any good shops I can completely trust. Not to 'toot' my own horn but the car is in really mint condition and I don't want anything to happen to it. Someone has already keyed and dinged my driver side door in the last month..

    Any help would be appreciated.

  2. #2
    Join Date
    Jul 2011
    Location
    Sacramento, CA
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    189

    Default

    I had an m10 e30 without a working fan and during normal driving the temp stayed under 1/3. Stopped, on a hot day it could reach 3/4 on the gauge. If you're on the freeway and your temp gauge is anywhere over 1/2, you should be concerned more with your radiator and thermostat.

    If you're still at 75% of the gauge then coolant is not cycling properly.

    Here is a thread with a similar issue.
    http://forums.bimmerforums.com/forum...d.php?t=681896

    Here is a link to a repair manual.
    http://www.bmwtechinfo.com/repair/main/027en/index.htm

    I would suggest bleeding your coolant, and inspecting all hoses. Replacement hoses for this engine are around $8-10 a piece.

    Good luck man. If you still haven't figured it out by Saturday, let me know and I'll swing by.
    Last edited by zxert; 05-09-2012 at 02:17 PM.

  3. #3
    Join Date
    Jan 2012
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    bay area
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    Default

    See that's what I'm thinking..I don't know if the coolant is cycling through all the way that's why I changed the thermostat but it didn't help and that's the third one I replaced.

    Thanks for the links. I'm going to order some hoses tonight but if you don't mind swinging by on Saturday, that'd be sweet. I have finals next week so I'm probably not going to have time to look at it anytime before this weekend. Thanks a lot.

  4. #4
    Join Date
    Sep 2011
    Location
    Los Angeles
    Posts
    38

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    u should just totally remoove the thermo, and your radiator is probably gettin clogged... is any coolant coming back to the expansion tank?

  5. #5
    Join Date
    Aug 2011
    Location
    Perth, Australia
    Posts
    161

    Default

    had the same thing happen to my m10 in an e21. i think when it got real hot it baked on or loosened all the crap in there and clogged something. i thought it was the thermo but made no difference as it was still running at bout 80%. chucked in some of that cleaner stuff, drove it for 20 mins, and when i flushed it the amount of crap that came out was amazing. after that it ran at 50% almost all the time, sometimes lower. also check that its not drinking coolant. you got white smoke from your exhaust?? i have heaps of friends that overheated engines, did the head gasket and ended up drinking all their coolant ever hour. start up the car with the radiator cap off and check that coolant is flowing and it isnt pissing out everywhere. hope this helps

  6. #6
    Join Date
    Jan 2012
    Location
    bay area
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    Thanks guys. I had my radiator tested and it's clogged therefore I'm on a hunt for a new one. That should solve my problem. The PO installed a new water pump so I don't have to worry about that. If the problem does persist I might have a leak in my head gasket that'll require a solid amount of cash and time.

    As soon as I get a new radiator and install it I'll let you guys know if I'm back on the road.

  7. #7

    Default

    i have 2 e21 m10 cars and depending how long it sat sounds like u may have a cloged water jacket or something in the block causing it to get hot? also maybe a bad rad i can't real tell without seeing it. btw nice to see a bimmerforums member over here :p

  8. #8
    Join Date
    Jan 2012
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    bay area
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    I'd love to see your cars! Post some pictures? It sat for a solid twenty five or so years so that could be a possibility. I did get my radiator tested and it is bad therefore I'm on the hunt for a new one but if my problem isn't fixed with a new radiator/or it keeps overheating after the replacement it would be more than likely that I have a bad head gasket with maybe a minimal hole or so. Will be replacing the radiator before I dig into anything else.

    My aux fan won't turn off at all...anyone know why that would happen? It also sounds like it's going bad/has a bad bearing.

    How did you know I was a bimmerforums member?! I just got into the forum game though so I'm pretty new to it. Plus I'm only 18 which can be discouraging to some therefore I'm not always taken seriously when it comes to car talk/advice...
    Last edited by Tom Cruise; 05-17-2012 at 02:26 PM.

  9. #9

    Default

    Hey man, just googled my car problems and came up with your thread! I'm having the exact same problems with my e21. It was running sweet for a year, until 3weeks ago it started over heating till it reached around 3 quarters! I got shit scared and pulled over to cool it down for the ride home.

    So I took it to my local radiator specialist, (I don't know why I didn't take it to the local Bavarian Mechanics) and they said it sounds like the thermostat. So I ordered a new one from Germany, took two weeks to get here and cost $145 nz.

    He replaced the thermostat and didn't change anything! He also tested the head gasket, main hoses, radiator all sweet. The only thing he hasn't checked is the water pump/hose. I'm fucking praying it's that!

    Did you have any luck with your heating problems?

    Cheers mate.

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