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Old 05-29-2002, 12:41 PM
Arthur Dalton Arthur Dalton is offline
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Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,768
Re: Befuddled ... engine temp ... after new Tstat

Originally posted by haasman
I am Befuddled:

My '91 300E coolant temp has been running at or just below 80c after ten minutes and more of driving at ambient temp of 60-70f. So I replaced the Tstat thinking this was the problem.

The car still hardly shows anything above 80c. Now I am wondering is it the Tstat or possibly a bad sending unit?


-How do I test the sending unit to the temp gauge?

Ohmeter at sending unit should read :
60C-110 ohm
80C-67 ohm
100C-38 ohm

-Is sticking a thermometer into the coolant reservoir a good test of the true engine coolant temperature?

Not really

Check that you have installed the right thermo.
Should be 87C for that car. That is start to open spec.

I checked the coolant and it does need more anti-freeze, it only goes down to about +5 degrees. Not a problem though here in N. California.

The least you should have is about 45/55 [af/h20].
A 50/50 mix will read -37C [ when hot]. -34F.

* The trivia question of the day is - When does C and F read the same ?
"Minus 40 degrees"

Any suggestions? Thanks as always.
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