My '05 325i (~80k miles) recently began dribbling coolant from the temp sensor housing on top of the lower coolant hose. I did a Google search and found some good information that allowed me to fix the leak *without* buying a whole new sensor from BMW, which is the only way to get an o-ring from them! Total time to fix was less than 15 minutes.
1. Here's a pic of the leaking sensor, taken from underneath the car. I'd already pulled the car up onto ramps in the front, and removed the lower tray. Sorry for the general crappiness, but I only had my iPhone handy.
2. From the top side, I used a flat-blade screwdriver to release the metal retainer clip and unplug the sensor. Then I squeezed the sensor release and pulled it out of the housing. NOTE: I did this on a cold motor, and lost very, very little coolant.
3. I used a small flathead driver to carefully pry off the the old green o-ring. I found dimensions on another site that equated to a #31 o-ring, which I found at Ace hardware for $0.59.
4. I popped the new o-ring on the sensor, re-seated it in the housing (it snapped right in for me), and hooked it back up. TIP: It might be obvious, but it's much easier to position the wire retainer clip on the sensor end BEFORE you plug it in... Otherwise you'll end up cussing and dropping it 5-10 times in the process. AMHIK. Anyway, I fired the car up, and watched the sensor for any sign of leaks as it came up to temp. No problems at all!
So, a pretty cheap and simple solution to what seems to be a common problem. Hope it helps!
JJ
-----------------------------
Current:
'98 M3/4/5
Past:
'05 325i Sport
'97 328i Sport
'87 635 CSi
'76 2002
'72 2002
Great post, I went through that trouble after replacing the whole cooling system.
But at the dealer, they only sell the sensor as a complete part...not the o-ring, how did u find the exact size at ACE? Lower hose sensor is 23 dollars not too bad.
High Mileage 325,xxx and counting...
BMW runs in the family
3-Series my whole life
e30 325i / e36 328is / e46 323i / 328Ci / 330Ci / 335i E92 / E46 M3
okartguy-THANKS, it sure did help me! edit: #31 o-ring also found at Home Depot-part#96745 sold in pak of 10 for $1.79
Last edited by STEALTHYZ4; 11-27-2009 at 01:06 AM.
Excellent write up! thanks
to the OP, or anyone else who has removed the temperature sensor:
I am trying to do this fix as I have a slow leak at the sensor. I can get the clip off and unplug it no problem. However, when I try to pull the sensor from the socket it is not budging. I am squeezing the prongs and pulling straight up. I tried this with my bare hands, a pair of pliers and a vice-grips. With the tools its hard to pull up because of interference from the A/C lines running across. What I seem to need is like a stubby pliers or much stronger fingers - hey, I have a desk job, I'm not a cow milker. Should it be this difficult, any ideas? I'd rather not take the entire lower radiator hose off, but its beginning to look like that is my next option.
Fahrer von Alpinweiß
It was bitter cold in NJ yesterday (about 14F) and when I left work to go into my car I noticed a small puddle of antifreeze in the front/center of my car. Do you think that this might be a result of a leaking O-ring? Please let me know. It looked like about 3 or 4 ounces of fluid.
This should help out as it seems to come up every now and then. Great job dude!!!
For a short term fix until you get the right o-ring.
Take out the o-ring carefully, get some faucet teflon tape and wrap it around the grove where the o-ring usually sit. I wrapped 3 full turns. Put the old o-ring back. I've mine for a week now with out leakage.
Yep, worked like a champ. Only took 5 minutes to replace...
Finally, someone actually posting a DIY in this section instead of asking a question which both the Sticky and the Section description explain.
Thanks
I used this thread to fix my car today. I had the O-Ring from a left over kit for a R-134 conversion.
Thanks!
Remember: Your life can be extinguished in ONE stupid moment. No one is invincible....
This thread saved me this morning. Changed the oil in the wife's E46 today and gasped when I saw the coolant leak. Quick trip to Ace and we're back in business! THANK YOU. I always poke around in the engine bay when doing oil changes, so I'm glad I did.
I had to do a similar emergency o-ring repair on my car, one of the o-rings on the upper radiator hose connection to the expansion tank got pinched or otherwise damaged during reinstallation. All I did, though, was soaked it in brake fluid to cause it to expand until I could get a replacement.
Thank you very much for this! I have a 6-series that uses the same exact temp sensor that was also leaking on my car. Very easy to do from the top on the E63 without the use of any tools!
okartguy, thanks for the write-up. I will be replacing the oring over the holiday. Again, thanks for taking the time out to write the post.
Happy New Years.
Just did a Temp Sensor ORing replacement using the Dorman #31 ORing.
Didn't Work.
It is still leaking and guess I need a proper "Green" BMW O Ring.
Called, Texted and sent Email to local dealer who stated: "Can't Buy The O Ring Seperately".
I believe I saw someone post a "BMW" Part Number for the Green O Ring seperately and/or some one who sells them.
Thanks In Advance
Doc
BMW part # 13621743299
Forgot I Found One
This thread was awesome. Thanks! If anyone else is having issues removing it (stuck). Just grab a flathead screwdriver, try to get it under the sensor and just twist it while pressing on the 2 tabs. Theres no reason to get under the car.
So, I installed a #31 o-ring, 9/16 od-5/16 id-1/8 thick, as a replacement on the coollant temp sensor, ultimately fixing the leak and turning off the SES light on the dash. All great!, however, now my temp guage shows max, my DSC light is on (meaning traction control off), my battery and oil lights are on as well, and also my emergency brake light is on--- all on the dash....I know your probably thinking the same thing, why the heck would any of those come on besides maybe the temp guage being maxed to hot? well, I figured maybe now that the whole coolant temp sensor needs to be replaced and that is what is causing the problems...and of course now i cant get the sensor out which is stuck with the new o ring....though it is still stuck i continued to think this over and thought maybe it's not a bad sensor as even before o ring replacement when it was still leaking, the sensor and guage seemed to be working fine...starting out cold and then sitting at 12 0'clock on the gauge once engine heated up...it was just the leak that needed fixing was my thinking and why i just did the o-ring replacement. I also bled the radiator system at the bleed cap to see if maybe air in the system was the reason the temp guage is all the way hot...nope. i then tried resetting the battery...nope, that didnt work either... Can anyone on here tell me why all of this might be happening and what i can do to fix the issue?
Sincerely and Thank You in advance,
Nick
Awesome thread... I followed leak in my car, and seems like it is the temp sensor. I have 2007 530I, and the part number for the temp sensor is diff (its 13621433077).
Few questions...How would you find the right o ring? Is it only dimensions, or also the material (it has to withstand heat and coolant)?
Thanks.
umermariner
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