Coolant leak

The way I see things is if it ain't leaking, don't mess with it. When you take the sensor, coolant does come out, lowest part of system

Originally Posted by hipertec

I wonder how the Home Depot O ring will hold up to the heat?
Can I just pull sensor out or will the coolant spill all over? Thinking about changing out just as a precaution..what do u guys think?

Sent from my Transformer TF101 using Bimmer

I have to agree with the comment surrounding will it hold up to the heat of the engine ? Rubber o rings can be of different material to stand up to the riggers of the engine, but for $3 it may well be an effective solution.............

Originally Posted by hipertec

I wonder how the Home Depot O ring will hold up to the heat?
Can I just pull sensor out or will the coolant spill all over? Thinking about changing out just as a precaution..what do u guys think?

Sent from my Transformer TF101 using Bimmer

Yeah, that was my first concern too. I can bet the BMW o-ring is of higher quality for sure. But it did give out eventually. I plan on keeping an eye on it to see how long it lasts.

As for your second question, you've got to keep in mind that coolant will definitely fountain upwards (almost instantly after pushing the two clips on either side of the sensor) because of a small pressure that builds up in the system. I think its best to do it in the morning after the engine has been turned off for several hours and is as cold as possible. Try to use your palm to direct the coolant flow downwards into a drip bucket. You don't want coolant spilling on the ground making its way into storm drains, etc. Its toxic stuff. And also make sure to rinse off any coolant spills in the engine compartment.

Alright, For those who are concerned about the O-rings at home depot, here is some additional research. Hope it helps:

I managed to find the approximate heat resistance rating of the O-ring sold at Home Depot. The brand I purchased is called Danco and its the #31 (click here). According to this page (click here), there are many O-ring materials with various resistance to heat and application suitability. Danco's o-ring is advertised as Buna N material (see here) which is supposed to have an operating temperature between -65°F to +275°F. So material wise it will hold up to heat just fine since water's boiling point is about 212°F if I haven't mistaken. Quality wise, I haven't been able to find much info on comparing Danco with other manufacturers but hopefully they aren't too inferior.

Well it has been over a month with the o ring from home repo and not a drip, that is car been driven everyday for work. We shall see how long these last but for three dollars for a pack of ten you can't beat it

Wow great work guys!!

Originally Posted by hipertec

I wonder how the Home Depot O ring will hold up to the heat?
Can I just pull sensor out or will the coolant spill all over? Thinking about changing out just as a precaution..what do u guys think?

Sent from my Transformer TF101 using Bimmer

The Danco Replacement O-ring that I have listed here is a tried and true method for fixing this temperature sensor leak issue. The E46 3-series temperature sensor is the exact same part number and they've been using this method of repair for years now with great success. Users only have to change the O-ring once and never again. Most of the time, the sensor itself will outlast the life of the vehicle.

Had the same issue, went to BMW, he said that they would change hose and sensor normally, I order the O-RIng, to make sure to get the right on. $3. I changed then also the coolant, because I mixed it with a another brand. Just want make sure not to ruin my internal sealing. Since then dry.

Wish I seen this before I went and bought the sensor from BMW for $45. They don't carry just the washer so I bought the entire sensor with new washer. This is great info. I will share with my fellow e65/e66 owners. Thanks guys!

Originally Posted by tampamark

This is all great info, I am happy that you guys are posting the cause and fix. The simple O ring is the way to go. If the sensor is good and the hose is good I wouldn't replace either since it is simple enough to do if and when they actually fails. The O ring is obviously the weak link in the system. Another BMW engineer fail!

Certainly if I ever have a lower leak this is the first part I would check.

+1

I got a low coolant notice last night. I was going to fix it in a week or so but may dive in this weekend armed with this info

I just did this o-ring replacement today, and was surprised at:

1) how little coolant came out (maybe 4oz) even though the level is full (engine stone cold)

and

2) how the sensor doesn't 'click' in or anything similar. I was left hoping it's in all the way. I guess that just shows how important that o-ring is to the seal.

Diagram a few posts up was money, helped me find the sensor with ease.

How are you guys getting to the temp sensor? Is any jacking of the car up needed? I am being told by the stealer that my lower rad hose is leaking and needs replaced on my 06 750Li. From everything I read on here I am going to assume only the o-ring on the sensor needs replaced and try that first.

Also, this would be on the bottom left side of the radiator when looking at the car from the front of it?

Thanks in advance.

Originally Posted by 3Pedals_6Speeds

I just did this o-ring replacement today, and was surprised at:

1) how little coolant came out (maybe 4oz) even though the level is full (engine stone cold)

and

2) how the sensor doesn't 'click' in or anything similar. I was left hoping it's in all the way. I guess that just shows how important that o-ring is to the seal.

Diagram a few posts up was money, helped me find the sensor with ease.

Follow up note. MY comment of the lack of a click became really relevant when I drove this around until it was hot and discovered that it SHOULD click in (the sensor), but I'd been too gentle with it. As soon as it got hot and pressurized, I had an empty coolant system.

So, if you do this mod, it is easy, just make sure you get that sensor all the way back in.

Originally Posted by trekwars2000

How are you guys getting to the temp sensor? Is any jacking of the car up needed? I am being told by the stealer that my lower rad hose is leaking and needs replaced on my 06 750Li. From everything I read on here I am going to assume only the o-ring on the sensor needs replaced and try that first.

Also, this would be on the bottom left side of the radiator when looking at the car from the front of it?

Thanks in advance.

I got at it from above. Doesn't seem like you can, but it will work.