318is - coolant leak - expansion tank - more

[Nickster51]

dear bimmerforum e30 gods,

my new '91 318is tries to overheat on me. temp gauge bounces around after reaching the 1/2 way mark (SI batteries or temp sender I'm guessing) so it's hard to tell how hot it's really getting.

where is the temperature sensor/sender? I've looked all over realoem and inside the car and can't seem to find it. I feel stupid. ( and I searched )

Basically I think it's overheating because once in a while I'll see coolant leaking under the car. I pop the hood and see it's coming from around the radiator cap / bleeder screw area. I think it's coming from the upper expansion tank o-ring, does this commonly/ever go bad? Does the expansion tank just pop off the radiator? I couldn't pry it off when I pulled the whole radiator so I quit before putting too much force on it.

Any and all help is appreciated guys...

[strad]

The temp sensor is about halfway back on the left side of the cylinder head. I can't remember if it's above where the intake runners attach or below. It is not likely that you'll be able to see it without removing at least the upper manifold.

The expansion tank can be removed. I've seen some people fix leaks by siliconing the hell out of where the tank attaches at its base. The o-rings on the cap do go bad from time to time.

[Wizard]

Check out this thread:
http://www.m42club.com/forums/showthread.php?p=25156

I think it starts at post #23