Operating Temp?
 

I have noticed since I picked up this car that the operating temp. seems a bit low. It never gets up to 80 on the gauge. It seems to hover in between the 40 and the 80. Mostly just above that "mark above the 40".

The records show that the cooling system was flushed and filled a year ago, new hoses and belts, but I don't see any mention of a thermostat?

Also, the fan clutch is seized on this car. The new one will be here next Tuesday.

Does anyone think that the seized fan clutch is causing the low temp?

Is there a procedure to test the temp sensor? With an ohm meter or other way. I searched and looked in the resources area. I did not see anything on it.

Most likely, you have a thermostat that is stuck in the open position. If you can confirm the head temperature with an infrared gun, you can rule out the sending unit and the gauge as the culprit.

Sometimes old thermostats will do that.

Even if the clutch is sized, the t-stat still determines the flow of coolant entering and leaving the engine. It is not THE problem, but it is A problem.

search a bit harder for the values for the sensor, someone recently posted them. You may want to remove it and test it in a controlled setting against a thermometer.

...although a light would certainly be easier.

Snook, I noticed I have this same "problem" on my 300SD. Any luck or new information? Is this a big problem? As my 300SD runs very nice!

I fixed this problem weeks ago. Forgot to post the results. Sorry about that.

The problem turned out to be a missing thermostat. Some one had "gutted" the thermostat and put just the ring piece back in the housing.

Anyway, I replaced the thermostat with a new Behr thermostat, a new fan clutch and put the old coolant back in there. It works like a champ now. It hovers right at 85 all the time now. And it warms up quickly (unlike before).

Snook, thanks again for stopping by and posting your update. I just recently acquired my 300SD, and haven't checked the thermostat but have one sitting in the trunk. Very interesting. I know what I will be doing tomorrow! Thanks!

No problem.

Be careful with that radiator drain plug. Mine damn near broke off trying to remove it. You may want to go ahead and get a new one before you start, just in case. They are only a couple bucks.