1990 740 station wagon coolant leak thermostat?????

Deeseven · Post by **Deeseven** » 23 Mar 2012, 15:36

I was driving yesterday, and then while stopped at a light I saw smoke coming from my engine, I quickly pulled over and noticed a pool of coolant gather underneath the passenger side of the engine compartment. I looked at the radiator for a leak, didn't see anything, I checked the hoses, nothing. Then I noticed the source it was a round hole on the passenger side of the radiator. I saw a plug kind of thing with blue and white wires attached. The plug either rattled loose or was ejected from the hole. I plugged it back in, replaced the coolant and things seem to be okay.

Can anyone provide insight on this for me. Do I have some kind of catastrophic issue brewing here?

Post by **billofdurham** » 23 Mar 2012, 16:37

The "plug kind of thing with blue and white wires attached" is the radiator temperature sensor. It is held in place by a rubber seal which is a one time fit only. If the sensor is taken out or, as in your case, falls out you need a new seal to put it back securely. It is best to use an OEM seal, probably the only time I would advise members to go to the dealer. If you can get two so you have a spare in case it should happen again. They are one time use only.

When putting the new seal in do not use any sealer or adhesive. Lubricate it with a soap solution. Insert the seal then the sensor which will expand the seal to make a good, tight fit.

You should now be considering why the sensor popped out. It could be due to overpressure so you should be checking the cooling system for blocked radiator, faulty hoses, failed thermostat etc.

Bill.

Deeseven · Post by **Deeseven** » 23 Mar 2012, 17:48

Thank you Bill.