In Reply to: 88 M3 Running Hot posted by Chris Schrimsher on May 03, 2000 at 12:17:13:
As far as your concern, the temp guage is for oil and you measured water (coolant), so no problemo.
I'd go ahead and replace the coolant reservoir cap as sometimes it causes the coolant to overflow unnecessarily if it isn't working properly. Cheap fix.
Good idea on testing the thermostat, it costs almost $100 for a new one. While you have the radiator out have them blow compressed air through it to get rid of the dirt/bugs that might be stuck to it.
Also a good idea is to check the wires to the aux fan switch as they get brittle and from the factory they are too short and sometimes break.
Good luck man.