really?? but the car is running so awesome. does a faulty thermostat give any other symptoms other than the cooler temp reading?? is there a way to test if the thermostat is bad before buying one..?? and how much is that part?? . :(

If the running temp is below 80 you should change it asap.
Neither the oil nor the metal parts are working below 80C

The only reason I hesitated to replace my thermostat was my unfamiliarity with this car. I understand that the operating temp is important; I just didn't know if MB thermo gauges might read low. The car was running great, plenty of warm air from the heater. But the gauge consistently read in the 65-70 range. Assuming the gauge is accurate, that is too cold for optimum engine perfomance, and could lead to extra wear.
With the new thermostat my car warms up more quickly, and the gauge reads right at 80 whether I'm on the freeway or in town. As I said before, the replacement was a really miserable job. But I'm glad that it's done, I'm sure that the engine will be "happier" running at the correct temp. I just hope I never have to replace it again!

My '96 E320 always runs between 90C(winter) and 95+C(summer) ... Check your thermostat... Hotter is better for your engine (but not > 100C) , IMO

was it thermostat that you change, or was it the temp sensor? thermostat is where a valve opens based on temperature and closes the valve (for water to pass thru) when its cold.

Oh really? Thats interesting.

One good thing, is if you ever had a fuel leak you have a less chance of ignition.... what, with the engine running so cool. :silly:

Normal running at 90C is likely not normal ... it is very interesting that some folks report running at 95C with peaks to 105-110C, but don't fix their engines ... this appears to be abnormally high relative to most folks that report running 80-85C almost all the time (normal ops).

It depends a lot on the engine and the engine bay, ambient temperature, and speed.

An M119 engine in a W124 engine bay is a tight fit.

Mine runs above 80 all summer, other than maybe during a sustained highway run (and even then).

check first the thermostat and see if it is working properly by taking it out of and testing with a pot of hot water and see if the openning and closing of the valve are working , use a temperature guage to measure the water temp and record.