temp gauge question 88 300e
 

unlike other cars i have owned, the temp gauge seems to follow engine temp very fast. seems to work, but when thermostat opens wham, drops quick. are these gauges different than other cars? from what i have read about these cars its ok to run near red at times. just not as steady as other cars. does not seem to wander just moves what seems quickly. first at 100c then down to 80c next time i look.
sorry about the way i wrote this but hard to explain
GREAT FORUM THANK YOU Rich

The thermostat is rated for 87C. This means it should start to open at around 87C and it will be fully open by around 102C.

Do you mean you could be driving along the highway and it will randomly drop from 100C to 80C just like that without any changes in engine or road speed? If this is true, this is not normal operation and I would suspect the thermostat is sticking and would replace it.

I had a bad sensing unit that behaved this way.

It should stay around 80, especially in this cooler weather.

thanks for the replys
 

well after watching my temp gauge yesterday,i noticed it moves faster than what i think it should. so first i'll try the sender. this should do it . if not, time for cooling system service with mercedes coolant amd thermostat . yes it does do 80=100 swing faster than expected.

thanks rich

WELL WELL WELL
 

i swap out my temp sender from my 88 190e and when i pull out the old sensor on the 300e(which was new from previous owner) i found sensor treads covered with a lot of silicoln. no wonder my temp was wierd. temp is more normal now. it's true that the temp does move more than most cars. i like this type of gauge better. its faster,more accurate . thanks for the info,won't worry so much sitting at a light
thanks rich

In slow stop and go driving even in mild weather the temp can easily climb to 100C, which is where the fan clutch tightens up.

Then you get of the freeway and at 70 MPH it drops back to 80 within a few minutes.

Duke