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Thread: DIY: Automatic transmission thermostat

  1. #1
    Join Date
    Aug 2008
    Location
    California
    Posts
    26
    My Cars
    325iT

    DIY: Automatic transmission thermostat

    I'm just posting a tip for anyone replacing their expansion tank.

    - below the expansion tank is a thermostat that could easily break when you pop off the old expansion tank. If your car has auto transmissionthis part is called "thermostat For auto trans oil cooler" bmw part #17111437362.

    Manual transmission cars might have a different part # but in either case there is a very delicate thermostat in the bottom of the expansion tank.

    Had i known to have this part on hand when replacing my expansion tank I'd have my car running by now but here it is saturday afternoon and i have to wait until monday afternoon to get the part from my local auto parts dealer. Then i'll need to finish the repair monday evening in the dark and in the mean time i need to borrow car!

    My advise, have this paet on hand before you attempt replacing the expansion tank.

    Cheers,

  2. #2
    Join Date
    Feb 2012
    Location
    Spokane WA
    Posts
    1
    My Cars
    2001 BMW 325i
    This happen to me as well when I was replacing my expansion tank. My car was down for a extra day and had to pay the sealership price for the extra part. As I remember it was around $100, so my advice is not to brake it in the first place.:-) The automatic transmission thermostat is housed in the hose under the expansion tank. To avoid braking it, make sure to lift the tank strait up and out when removing it. Any side to side motion and it can come into contact with the brittle plastic of the Thermostat. This is easier said than done of corse, as you must wiggle the tank to free it. Almost glad that mine broke, as the plastic of the thermostat was SO brittle that it would just crumble in my hand. It was also a pain to get the bad thermostat out. Had to pry mine out with a flat head screw driver. Hope this saves somebody a little time and $.

    P.S. First post!!!!!!!!!!!!!!!!!

  3. #3
    Join Date
    Nov 2010
    Location
    Colorado/USA
    Posts
    12
    My Cars
    2002 BMW 325xi
    I had the same experience with the auto. trans. thermostat. It just disintegrated in my hands, as the man at the BMW parts counter predicted. I was buying an expansion tank at the dealership and he suggested that I buy the thermostat too. I bought it, hoping to be able to take it back the next day. As predicted, the thing just crumbled and I was glad to have a replacement.

    I've attached a photo of the broken part.
    Attached Images Attached Images

  4. #4
    Join Date
    Mar 2010
    Location
    monroe
    Posts
    160
    My Cars
    92 bmw 325i
    Id this on manual transmissions too?

    Sent from my ADR6400L using Tapatalk

  5. #5
    Join Date
    Jan 2008
    Location
    Louisville, KY
    Posts
    10,141
    My Cars
    turbo m3
    Man, I wish I would have searched this section before I replaced my expansion tank.

    Needless to see, one side of the t-stat was broken on my car too, so I had to wait for the part to arrive.
    This is my signature....

  6. #6
    Join Date
    Feb 2012
    Location
    Hyannis
    Posts
    21
    My Cars
    2001 330CI Coupe
    That happened to me too...............but i was in a spot so i left it out. Car runs fine .
    Is this Bad ?????????

  7. #7
    Join Date
    Feb 2012
    Location
    fayetteville, NC
    Posts
    7
    My Cars
    2004 BMW 325i
    any word on how the car runs without it? i just broke mine and don't want to pay $130 for a new one at the stealership.....

  8. #8
    Join Date
    Apr 2012
    Location
    ft lauderdale
    Posts
    1
    My Cars
    2004 bmw x3 2.5l

    to with or without, that is the question

    the car runs better without

  9. #9
    Join Date
    Jul 2008
    Location
    Troy, OH, United States
    Posts
    670
    My Cars
    94 530i M60 3.0L V8

    Question

    Does the CEL throw a code when this thermostat is broken ?
    Lead, Follow or Get the Hell out of the Way!

  10. #10
    Join Date
    Oct 2010
    Location
    colorado springs, colorad
    Posts
    110
    My Cars
    2001 bmw 330ci
    No problem, I had mine gone over a year. Drove from COS to LAS 1600 round trip. Found out today, had a leak at the radiator.

  11. #11
    Join Date
    Dec 2009
    Location
    DFW
    Posts
    1,495
    My Cars
    99 R1100RT
    I yanked my expansion tank a bit too much force, too, and broke the thermostat. Had to wait a few days for it to arrive from AutohausAZ, but since it came in the same box as the radiator, I haven't lost any time.

    Now... My dilemma is this: The thermostat broke so that the lower part of it is still attached to the plastic piece that was attached to the radiator. How do I get it off there? Picture attached.

    I have tried prying it gently, but I guess the O-ring that seals it is not letting go too easily. PLUS, I don't want to break the anything on the plastic piece.

    If push comes to shove, I can just try breaking the thing, of course, but would really prefer getting it out in one piece.

    Any suggestions?


    EDIT: Never mind the removal... How about getting the new one in without braking anything??? I can get it so that it is about 1/2" from where it should be but then it stops and doesn't want to budge.

    I even tried putting some grease on the o-rings and the sides, but still the last 1/2" remains.

    EDIT #2: For some reason the o-rings are just way too big to get the thermostat to fit properly. Swapped the o-rings from the old one and it slid into place with no issues at all. Hmmm...
    Last edited by TexFinn; 06-14-2012 at 10:46 PM.
    1999 BMW R1100RT
    2005 MC C230K Sport
    2007 Chevy Silverado Crew Cab Z71
    2010 Chevy Tahoe LT2

  12. #12
    Join Date
    Oct 2009
    Location
    Tucson, AZ
    Posts
    8
    My Cars
    1996 bmw 328ci
    Hey, TexFinn.
    Fought with trying to get that thermostat in last night. I may try the old O rings also, the new ones are pretty large....I wonder if it's because I ordered the cheaper (non OEM) thermostat?...though they look exactly the same online. I also couldn't understand how that little plastic clip piece on the side was supposed to fit it, appeared to be in the way, probably because the Orings are just too fat like you mentioned and wouldn't let it slide in all the way. I think I will just see if it fits together with the Orings off, and if it does I'll take it back apart and try to salvage my old ones or try some extra ones that I have that are similar. Wow, I wish it was easier to parts locally.

  13. #13
    Join Date
    Jun 2014
    Location
    montreal
    Posts
    1
    My Cars
    bmwx3
    What could happen if you take out this thermostat?

  14. #14
    Join Date
    Nov 2007
    Location
    Benton Harbor, MI
    Posts
    49
    My Cars
    2004 325xi
    Don't know if anyone is still watching this thread, but I ran into the EXACT problem being described, & finally got the bottom half of the busted thermo out of the expansion tank bracket. Cleaned it out & reassembled everything, and have no leaks - temp is great, but the gear with the exclamation point (transmission warning) is still on, and the car drives OK but shifts & downshifts very hard. I was hoping that removing the busted thermo would take care of that light, but no go. Tried the reset trick - Park, handbrake, key off, wait a few, then re-start, but no change. Can this be reset with a tool at a service place? How about taking the neg cable off the battery to dump the whole system? Any help would be appreciated...!

  15. #15
    Join Date
    Jun 2013
    Location
    West Hills, California
    Posts
    1
    My Cars
    2001 z3 Coupe, 2003 325i

    Reset

    Quote Originally Posted by deadjohn View Post
    Don't know if anyone is still watching this thread, but I ran into the EXACT problem being described, & finally got the bottom half of the busted thermo out of the expansion tank bracket. Cleaned it out & reassembled everything, and have no leaks - temp is great, but the gear with the exclamation point (transmission warning) is still on, and the car drives OK but shifts & downshifts very hard. I was hoping that removing the busted thermo would take care of that light, but no go. Tried the reset trick - Park, handbrake, key off, wait a few, then re-start, but no change. Can this be reset with a tool at a service place? How about taking the neg cable off the battery to dump the whole system? Any help would be appreciated...!
    Deadjohn

    That exclamation mark means there is something wrong with the transmission/transmission system. You can go somewhere and get it cleared, but for the price of that, you could get the device yourself and find out what is wrong with your car. Go to Fleabay and look up OBD BMW diagnostic cable. It comes with the software the dealers use to diagnose your car. Using INPA you can get rid of the code but before doing that, I would find out what is wrong with it first. You can run a diagnostic prior to clearing the code. If it recodes really fast I would check the wiring first and the sensors next. Anyway, the cable and software is around $45 and will come in handy if you keep your car.
    Last edited by mescalero1; 06-29-2014 at 02:33 PM.

  16. #16
    Join Date
    Jun 2012
    Location
    Boca Raton & Salisbury NC
    Posts
    47
    My Cars
    2001 325i
    Thermostats regulate the cooling, I wouldn't drive with a busted thermostat on my engine or my transmission. But if you have an automatic, you have a good excuse to convert to a manual when it overheats and takes a crap. Hopefully you have set aside funds in advance.

  17. #17
    Join Date
    Mar 2016
    Location
    vallejo
    Posts
    1
    My Cars
    2000 740 i

    How????

    Quote Originally Posted by x3bimmerkit View Post
    the car runs better without

    how did you bypass the thermostat? how do you just leave it off? doesnt the return line go into the thermostat? please let me know

  18. #18
    Join Date
    Aug 2017
    Location
    Kentucky
    Posts
    2
    My Cars
    Bmw, x5 2006
    Did you ever fix this problem.... I am having exact same issue. Thanks

  19. #19
    Join Date
    Feb 2008
    Location
    orlando
    Posts
    56
    My Cars
    535i

    dont take shortcuts

    guys please dont take shortcut to remove the thermostat.
    i bought the entire reservoir and that comes with the thermostat. buy the Dorman brand from pepboys and it came with the sensors and everything.
    watch my video which shows the parts and also how to remote the stuck thermostat during replacement of the reservoir.

    https://www.youtube.com/watch?v=y9skaSjcLKM

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