Coolant Leak at Lower Radiator Hose Temp Sensor
 

I have a 2006 3.0i. I discovered I have a small leak that appears to be coming from the temp sensor on the lower radiator hose. After looking on line at the part it looks like it can be removed and it has an O ring. I suspect the O ring has hardened. It looks like it can just be removed, a new O ring installed and the sensor reinstalled. Anyone have to do this? Were you successful or did the sensor plastic break or fall apart? I had that happen with the trans cooler thermostat.

If it's a part that's likely to break I'd rather just go ahead and order a new one as if it breaks my car will be down until I can get a new one and I need it for work. I don't know if the hose has ever been replaced as the records are incomplete. The hose looks and feels in good shape. If I go ahead and order the sensor I'll probably order a new hose as well.

Thanks in advance!

Leaky o-ring. I just wrapped mine with Teflon

The o-ring is easy to change and will not be that hard. It is available separately from the sensor. There is a chance that part of the problem is that the plastic housing portion that it sits in is slightly warped though as well. The teflon, as andrewwynn suggested, works well and is really quick as you don't even need to remove any coolant if you let the car cool down and don't take off the cap.

I replaced that o-ring, along with the lower radiator hose (and a bunch of other stuff) recently on my '01 3.0i with 186k miles, and there were no problems. Plastic things un-snapped like they were supposed to, etc.

And BTW, my existing o-ring was fine, nothing leaking, but I put the new one in anyway. As with all those o-ring fittings, a little silicone grease or lubricant will help it seat better, which will help things seal better.

Well, I'll say I did not try it with the car cooled down and the cap still on. Pretty cool if that is enough to keep the coolant from coming out. :thumbup:

Thanks guys. I'm getting a new o ring. Hose looks to be in good shape. I'm going to try doing it when cold with the cap on to see if 80stech trick works. It will be great if it does.

Same leak happened when I was changing all my coolant hoses. It didn't leak before I unplugged it, so unplugging it broke whatever deal was keeping it from leaking: the o-ring was cut. I couldn't find it sold separately, so I got a whole new sensor (from FCP Euro I think) which wasn't that expensive.

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I use the 50-cent O-ring from hardware store.
It works fine.

Detail in here:

https://www.bimmerforums.com/forum/s...g-for-59-cents

Same happened to me a few months ago - 2006 3.0i with 110.000miles.


New o-ring fixes it, no coolant drainage if you work on a "cold" car with the expansion tank cap in place.


Bought the O-ring: 8x3mm - fits perfectly.


It's a nice & easy job to do...

I checked my notes, and here's the o-ring I bought when I replaced that lower radiator hose:
https://www.rmeuropean.com/Products/...0-MFG1190.aspx

Calls itself 8x14, which is 8mm ID, 14mm OD, 3-mm thickness

That is good info :) I think there is a thread with an o-ring list somewhere that maybe we could add that to.

You can get a 10-pack on Amazon. I bought some ansost track of them (tiny bag). Mine is still using the Teflon fix since December


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Would love that. Managed to find the O ring at FCP and ordered it. Couldn't find the actual dimensions so I could source locally.

8x14x3 as oldskewel said.

M3x8 Viton O-Ring, 75A Shore Durometer, Round, Black, 8 mm ID, 14 mm OD, 3 mm Width (Pack of 10) https://www.amazon.com/dp/B005RUSWCG..._o5JQBbR468PF1

I had no luck with local sourcing. I bought a ten pack on Amazon and promptly lost the tiny bag!

I made a rubber finger from a rubber glove and a piece of foam to plug the hole when I removed the sensor to stop the leak. (think finger in the dike) (carful how you spell that: DRASTICALLY different meaning!)

I wrapped 3 turns of Teflon around the obviously flattened o-ring (now more like a square cross section.

I would recommend replacing that o-ring about every 100,000 miles if you still have the lower hose.

I have two of these so I have "a spare part of everything" so I don't replace much before it's broken. Say my wife blows her lower hose on the freeway I can get a ride from a friend with my lower hose in hand and avoid a tow. (Oh and a big hug of water/coolant depending on ambient temp.

Wife's car is currently using my original fuel pump I'm using the new one similar reasoning. Her original pump failed about 140,000 miles right where I'd expect for a city driven X5.

I noticed my sensor was leaking at the exact same spot. The hose probably has 10k miles on it tops, but I didn't replace the o-ring when I overhauled the coolant system last time.

I took that part number oldskewl gave and put it into FCPEuro as Fifty150 mentioned.

Search 091158010 and it will turn up.