Here is my problem. Whenever I start my car, 85 380SE, the water temperature will rise slowly up until reaches approximately 110 C. Then, quickly drops to about 90 C. My question is this temporary temperature of 110 C too high or is it ok?

Mike

Mike,

Your thermostat is probably sticking. There's a little arm on the t-stat which catches on the housing and causes the immediate temperature increase then decrease to normal. Solution is to replace the t-stat and either file the housing a little or cut the arm off the new thermostat. That oughtta take care of your problem!


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Rgds,
Aaron Greenberg
MB technician
Precision Motorcars, Cincinnati, Ohio
'67 250SE Cabriolet
'77 450SL
'80 300SD
'85 380SE
'89 420SEL
'93 300E 2.8
'74 Jensen Interceptor Mk.III
'81 DeLorean DMC12
'85 BMW 745i Turbo

Aaron,

I thought about that but couple months ago I replaced thermostat, water pump, and temperature sensor.
I don't know how harmful is driving this way?

Mike

My 380 se has always done this. My mechanic says it is normal to boost up then drop to normal. So far no problems after 4 years.

The rate at which the temp drops after the t-stat has opened is a function of how fast it opens at rated temp. If it starts to open at 90, your temp may go up a bit higher then drop as the stat fully opens. If you want to experiment. Take out the stat and see what the max temp is. You're in a warmer area of the country so this shouldn't be a problem. Some open slower than others. If it does drop back down to 88-90, then you're OK. Be happy, don't worry.

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Jeff L
1987 300e
1989 300e
1987 BMW 325