Cool running 91 300te, what is normal temp?

[robaincltnc]

What is the normal operating temp on this car? It seems as it is low on my car. Just over 60c usually. Also, my heat doesn't seem to be as hot as it should be. I can open it up to full heat and it warms but never gets HOT. Any help is appreciated.
rob

[glenmore]

My 1991 300CE runs at 85-90C, a little warmer now with a new thermostat. Prior to this it seemed to run too cool, barely 80C. Then the thermostat failed in the closed position and I overheated and this subsequently led, I believe, to a failed head gasket.

A thermostat is cheap and easy to change.

glenmore
1991 300CE
2000 C280
1990 LS400

[robaincltnc]

Originally Posted by glenmore

My 1991 300CE runs at 85-90C, a little warmer now with a new thermostat. Prior to this it seemed to run too cool, barely 80C. Then the thermostat failed in the closed position and I overheated and this subsequently led, I believe, to a failed head gasket.

A thermostat is cheap and easy to change.

glenmore
1991 300CE
2000 C280
1990 LS400

Understood. I'll pick one up today. Can anyone give me instructions for a novice dyi'er?

[glenmore]

Get a good quality one like a Behr or a Wahler. They should come with new gasket.

The manuals always tell you to first test it in boiling water to make sure it works, but I have never done this.

Get a benz parts catalog from ************************. Their exploded parts pictures come in handy. Of course, support this site by buying from Fastlane.

On my car, the thermostst housing is secured with three bolts (only 10Nm torque).

Note orientation of old thermostst, ball valve should be situated at highest point when installed.

glenmore
1991 300CE
2000 C280
1990 LS400

[softconsult]

First engine must be reasonably cool. You are going to lose some coolant, so you will also need some of the proper coolant on hand, mix 50 /50 with distilled water. If you have Green Coolant, then top off with Green. Hopefully it has the proper Mercedes Coolant or ZerexG05, sort of amber colored. If it does then use that.

You need a 1/4 ratchet, 6 inch extension, 10mm socket. 3 bolts. Expect the cover to be slightly tight. Tap and twist it free it up. Do not resort to hammering a screwdriver blade in there. Remove the cover.

Notice which end of the thermostat is pointing up. Remove, replace and put is back together using the new rubber O ring. The torque figure of 10nm is no doubt correct, but you would need a torque wrench. I do it by feel. No way to verbalize that to you.

Top off coolant at the expansion tank.

Your temp guage should then be around 1 needle width or so above the 80 degree mark and your engine will be happy.

Steve

[robaincltnc]

works beautifully, thanks for your help!