My 1985 300D Turbo's temperature readings have been puzzling me. It rarely gets to 80 degrees,which is supposed to be OPTemp, correct me if im wrong. If it matters, the ambient temp. around here has lately been around 60-65 degrees in the afternoon. I don't think it makes much of a difference though, since the temperature reading has only been 80 degrees in the hot summer.

I also noticed that our 1986 300SDL took a much shorter time to warm up. So my first instinct pointed to a faulty temperature sensor. But i really have no idea where it is or what it looks like. So for the hell of it I checked the radiator fluid. I took off the cap and the rubber gasket attached to the cap is falling apart and torn up. So's i gots some questions

1.)How vital is the gasket's structure? Does it have much of an effect on my temperature readings, warm up time, and consequently, fuel economy?

2.) Do i need a new radiator cap or can i just replace the gasket? Or should i just replace the cap anyways after 20 years?

3.) Anyone know how much would the MB dealer charge me for a.) radiator cap with gasket, and b.) just the gasket?

-Ara

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1985 CA 300D Turbo , 213K mi

Hm. Need some help. I replaced my radiator cap and the temperature sensor, but the water temperature, with the engine fully warmed up, reads like 0.3 centimeters below the 80 degree mark. What could be the problem? It must not be the sensor. The only thing I can think of is the green coolant in the coolant reservoir... plus who knows how long it has been in there. Could that be the cause of my temperature readings?

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1985 CA 300D Turbo , 213K mi

Maybe I'm missing something here, but have you considered the possibility that the thermostat might be faulty?

Your lucky as you feel your temperature is too low. Nothing really expensive to repair. Another thread presently running may give you some insite. Same thread makes a suggestion on how to read actual temperature. If you are really too low than a simple thermostat change will most likely up your operating temperature. Also have heard some of these cars normally run at about 80celcius indicated as well. If you are running at 80 fairenheit then of course most likely the thermostat is open and defective. The rad cap needed replaced anyways so nothing lost there. (these cars come with two differently calibrated temp gauges one in fairenheit and the other in celcius) The coolant type is not creating the low temperature reading no mater what type or age. About now I would get actual temperature read with engine hot to compare it to your gauge before spending any more money.