Hi,

I recently replaced the coolant and thermostat on my 97 C 280.

It is an 87C t-stat, but at first it took an engine temp of 95C to get it to open. With outside temps of 70F at highway speed, the engine runs 90-92C. With the old thermostat, which I figured I would replace for insurance when I had the coolant out anyway, the temps under these conditions were 82C.

My question is if there is some type of "break-in" with the t-stat. Will it eventually correct itslef to run at the correct temp or not? The engine temps at first were even higher, but they have since lowered 2-3 degrees. Or is this error allowable and no big deal?

Thanks a lot.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record

Ali:

I'm not familiar with your model of MB; however, there are some basic principles that apply across the board.

- Many T-Stats have an air bleed valve on them that must be positioned at the highest level.

- You may have introduced air into the system when the coolant was changed.

- What mixture of coolant-to-water is now being used vs. before? Excessive coolant can cause increased temps. as coolant does not disperse heat very well.

Regards.

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Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

You mean coolant doesn't cool?

I did position the thermostat correctly and I am absolutely certain that their is no air in the system. I properly bled the system, 9 quarts came out and 9 quarts went in. Also, I used the same concentration of coolant as before.

I am positive that the higher temps are only related to the thermostat. When driving down the highway and stopping, I can feel the radiator and see that towards the bottom of the radiator is cold, so I know that the thermostat is controlling the bottom end of the temp higher than it is supposed to.

The car does not overheat at all under any condition, it just runs warmer than the thermostat is rated at highway speed. In traffic temps, etc. are the same as before.

__________________
Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record