Engine Operating Temperature

[pberku]

I just changed the water-pump housing and the water pump on my '95 E300D. The reason being is that the water-pump housing was completely pitted and had many small holes allowing coolant to leak out. The water pump itself was OK but was changed since everything was already apart, and I believe that it may have been the original water-pump. Both parts are original Mercedes parts. The Thermostat, which is only 1-Year old, was not changed.

Prior to changing these parts my car run at a relatively steady 90C. After the above work was done it now runs at a relatively steady 80C, and takes longer to reach this temperature.

Which of these temperatures is the normal operating temperature for this car, and why the sudden change? Is it possible that the Thermostat was not installed correctly? Or am I better off now than I was before. I should also add that before the top Radiator hose was rock hard at the 90C temperature. At the new operating temperature it is somewhat software.

Thanks

Phil

[leathermang]

I don't know about your late model car... but my 1980 240 runs at 80c all day long.... now the trick is that the thermostat has two openings and different temperatures for each of them on my car... I have posted that info in one of the ' how to replace thermo' threads....
The lower number on my thermo is 80c....

[billrei]

If the metal in your cooling system degraded that fast I would definately make sure you are using the MB antifreeze with distilled water. Make sure your system has no trapped air. Sounds like the flexing hose is full of air which could affect your temp reading.

[ktlimq]

In my 1992 300D, coolant temp gauge usually reads 90 C. It went to 95 C last summer when A/C was operationg during city driving.
When A/C is not operating and the car is driving at 50 ~ 70 MPH steady speed, the gauge reads 85 C.

Because the manual says that 80 C is normal operating temperature, I asked about this to a dealer. The dealer tech said that that temperature range was OK, and it was not worth putting money due to this matter.

Although an indi (Hatch & Sons, MA, USA) said, about a year ago, my water pump and thermostat were leaking, other mechanics did not suggest replacement of these (a mechanic did pressure test and found no leak). Coolant level is quite steady.