Coolant Temp Sensor O-Ring is a BMW Part Number

Hey all,

Did a search and nothing has been posted here.

I am referring to the sensor located in the lower radiator hose. If you have DIY-ed your cooling system, one way or another you might have purchased a new sensor because there is no way of just replacing the o-ring. There is a buna-N replacement found in hardware store, which can be a bit of snug fit but not a perfect fit.

But I found the right BMW part number for this o-ring: 13.62.1.743.299

Yes that's right. You can now just replace the o-ring WITHOUT having to buy a new sensor. Will set you back a whooping $1. This is the same o-ring used to replace the IAT sensor on slightly older E46s. These E46s have IAT in the manifold instead of a 5-wire MAF.

Here's a pic. Nothing too exciting really.



Now generally speaking, most of the o-rings found in hardware store (for plumbing and such) are Buna-N not Viton. The material if you compare side by side with this BMW o-ring is very different. Viton has better oil, temp characteristics compared to Buna-N. There are no hard rules as to identifying which material based on color, measure (metric/imperial) or feel of the material. But my educated guess is that this green metric o-ring used by BMW is most likely Viton.

Wow was that ever insightful and right on time! I came out of the office today to find a nice puddle of coolant under my car and pinpointed it to have come from the temp sensor. A quick trip to the dealer up the road and I was back in business. I can't thank you enough for posting this!!!!
-Jay

Arghhh I wish I had known this 6 months ago when I did my coolant system overhaul!! Oh well, an excellent find!!

Please put this in the wiki.

My sensor is leaking. How do I remove it? Does it just pull out or do I have to turn?

Originally Posted by charlesberry

My sensor is leaking. How do I remove it? Does it just pull out or do I have to turn?

You may have to wiggle it a bit, but it should pull straight out. I just installed a new one last weekend and as I recall it pushed straight in..... no twist. Just be sure to unclip the electrical connector at the top, as you don't want to risk damaging it when pulling.

Very good information. Thanks.

Originally Posted by Solidjake

Very good information. Thanks.

And a very good source as well.

Hello VINCE!!

Thanks!! I really appreciate this. Was driving home last night, coolant light came on.
Got the car in the garage and took a look and found the leak. I'm driving to Boston next week and need to get this taken care of. Again - thank you for the info.

Chuck

On the flipside, if you do replace the sensor, make sure to also order a new O-ring. I did mine and didn't realize I needed to replace the O-ring as well and ended up with a leak after installing the new sensor.

I would have expected a new sensor to come with a new O-ring. I did a cooling overhaul a while back and had another issue with the sensor. I bought a new lower hose and tried to use the original sensor. It leaked like crazy so I am still using the old hose and original sensor.

Will check with my dealer on the O-ring. Good information!

Hi, I did a quick remedy of stopping the leak in my temperature sensor by wrapping around with teflon tape. It works ,,it is over a year already and no leaks at all. You can buy teflon tape in any harware store , it is used for sealing the plumbing threads.......

I opened a thread on the E39 side asking for someone to measure the ID and thickness of their coolant temperature sensor green o-ring ... but maybe we can team up to find the answer to these questions:

Are we sure the the right material is BUNA N (or is it Viton)?
Are we correct in the part number being 13.62.1.743.299?
Is the correct size of the original o-ring 8.0x3.0 (8mm ID, 3mm thickness)?



REFERENCES:
- Coolant Temp Sensor O-Ring is a BMW Part Number
- DIY - Temp. sensor coolant leak repair
- E46 Cooling system temperature sensor part number
- Replacing the coolant temperature sensor DIY
- Recommended parts list for a cooling system overhaul
- E46 lower radiator hose coolant temperature sensor
- BrassCraft 0567 replacement for coolant temperature sensor o ring
- BrassCraft and Viton replacements for coolant temperature sensor o-ring
- Coolant temperature sensor o-ring dimensions
- Replace coolant temperature sensor o-ring with viton from macro rubber

This is great! I went to Lowes and Advance Auto, and neither of them had an o-ring that was the right size. This sure saves me a lot of hassle. Thanks!

Originally Posted by Mr Paddle.Shift

Hey all,

Did a search and nothing has been posted here.

I am referring to the sensor located in the lower radiator hose. If you have DIY-ed your cooling system, one way or another you might have purchased a new sensor because there is no way of just replacing the o-ring. There is a buna-N replacement found in hardware store, which can be a bit of snug fit but not a perfect fit.

But I found the right BMW part number for this o-ring: 13.62.1.743.299

Yes that's right. You can now just replace the o-ring WITHOUT having to buy a new sensor. Will set you back a whooping $1. This is the same o-ring used to replace the IAT sensor on slightly older E46s. These E46s have IAT in the manifold instead of a 5-wire MAF.

Here's a pic. Nothing too exciting really.


Now generally speaking, most of the o-rings found in hardware store (for plumbing and such) are Buna-N not Viton. The material if you compare side by side with this BMW o-ring is very different. Viton has better oil, temp characteristics compared to Buna-N. There are no hard rules as to identifying which material based on color, measure (metric/imperial) or feel of the material. But my educated guess is that this green metric o-ring used by BMW is most likely Viton.

I bought one last week from the dealer $42.xx with the o ring. Replaced the sensor and the leak is stop. I could have saved $$ had I seen this a week ago.

We have them available for anyone who is still in need...

Click HERE for more information.


Please let us know if you have any questions! Feel free to shoot me a PM or email.

Best,
Joe

Originally Posted by ECSTuningJoe

We have them available for anyone who is still in need...

Hi Joe,
This is wonderful. Do you stock them from outside of BMW or do you use the part number of the intake manifold o-ring. Just curious how you do it.

BTW, in the alternator & cooling system thread ... I measured a new FAE coolant temperature sensor o-ring at 0.330" ID by 0.115" thick (i.e., 8mmIDx3mmThick) which is the same 8x3 size as the BMW PN 13621743299 intake manifold air temperature sensor. It apparently fits all E39 and E46 vehicles; I'd recommended adding it to your cooling system overhaul recommended parts list.

Originally Posted by bluebee

Hi Joe,
This is wonderful. Do you stock them from outside of BMW or do you use the part number of the intake manifold o-ring. Just curious how you do it.

BTW, in the alternator & cooling system thread ... I measured a new FAE coolant temperature sensor o-ring at 0.330" ID by 0.115" thick (i.e., 8mmIDx3mmThick) which is the same 8x3 size as the BMW PN 13621743299 intake manifold air temperature sensor. It apparently fits all E39 and E46 vehicles; I'd recommended adding it to your cooling system overhaul recommended parts list.

We source all of our Genuine BMW parts BMW directly!

Thanks,
Joe

Just to be 100% accurate...it's not the same o-ring, but very, very close to the original sensor o-ring. I just returned from the bmw parts department where I picked up the new o-ring and the parts guy brough the brand new sensor, took off the original o-ring and we compared the two. They are slightly different color and I believe different material. The new one looks slightly thicker resulting in larger outer diameter and the inner diameter looks slightly smaller. But they are really, really close. So, there is no reason why the new one would not be successfully used as a replacement, but again to be 100% accurate it's not a direct replacement...

I am trying to replace the coolant temperature sensor in my 2000 328i which is located in the lower radiator hose. As many other posts have stated, mine is leaking. However, when I went to do the "easy" swap, the old sensor won't come out. I pinched the 2 little levers on the side to release it and pulled but it won't budge. Any ideas how to get it loose? Also, does this sensor have any control over the electric fan cooling the ac?

Holy crap, I wish I'd seen this thread a year ago. Stealership only sells the sensor with the o-ring, at a hefty price (~$40?)

Anyway, to your question, shobbs: This should be pretty easy to take out, compared to other items in normal DIY. Make sure the lead is off first, so you know what you're dealing with and don't frig it up. Then, get a flashlight in there to make sure you see what your are squeezing to pull it. And, make sure you aren't doing the classic passenger pulling-the-handle-before-unlock routine with the side clips. They have a good bit of travel, but need full disengagement prior to pulling to avoid clip flex.

Originally Posted by ECSTuning

We source all of our Genuine BMW parts BMW directly!

Thanks,
Joe

Now tell them how much you will charge them to ship it to them.

I didn't really expect them to respond to that one.

Is the pictured Sensor the same as the Sensor on the top of the Bottom Radiator Hose ?
Thanks

Originally Posted by ECSTuning

We source all of our Genuine BMW parts BMW directly!

Thanks,
Joe

ECSTuning Shows A Diagram For The Sensor at the Intake.
Are both that Senor and the one on top of the Radiator hose the same Sensor [hense same Oring].

I just replaced the ORing on the Sensor on top of the Radiator hose with a Dorman 31.
It did not stop the leak and the dealer says they "Don't sell the ORing seperately"

Thanks In Advance !!