Hello Experts,
I have a 2002 e320 station wagon 4matic with 97k miles. My engine temperature has always been 79C and did not fluctuate. Recently, the temperature went up to 100C while driving but then came back down. So I changed the thermostat using the same OEM part. Now temperature stays at 87C. Looked at my old thermostat and the temperature setting on that is 87C. So, why was my engine temperature at 79C with my old thermostat which was set at 87C?
With the new thermostat, my engine runs at 87C which is the correct temperature according to the thermostat. But I wonder if it should be running at 79C like it was with the old thermostat?
Thanks.

 

Tstat is set to 87c,however that is full open and subject to cooling demands on the system cooler weather will have it around the 80c mark warmer weather and more demand will have it around 85-90.hot weather and ac in traffic could have it around 100c for short periods.Check your coolant condition and flush per the service intervals with zerex go5 and 50/50 mix for best protection.
ohlord

 

The wax canister, or other mechanism, for opening the stat may have become defective on your old stat.

Best way to determine if old statis faulty is to put it in a saucepan of water and put it on the stove with a temp gauge in the water. It should be opening by the time it gets to 79 degC.

As ohlord states the thermal output of the engine and the effectiveness of the radiator may exceed balanced conditions at 79 deg C due to high ambient, towing, heavy load etc in which case a balanced condition will be established at a temp greater than 79 deg C.

If the vehicle is "old" the effectiveness of the water pump and potential blocking of the small waterways in the engine block / head and radiator can give rise to more serious conditions causing thermal balance to be achieved at a temp greater than designed, but if the system has always been filled (and refilled periodically) with the correct coolant, this scenario should not be a problem.

Stuart

 

Thank you ohlord and snanceki.
I am going to try to flush and fill the coolant. Maybe that will get the temperature down a bit. Also, I have not done it even once and I am at 97k so it is probably about time.

 

Hi,my sugestions is that after you change thermostat and flush system try clean radiator with strong air presure inside and out,sometimes after while is lot dirty stuf and dust inside radiators blocking air from outside to get thru ...

 

No air,you can use chemical flushes or a cup of powdered tide laundry soap and flush till clean.when refilled add a bottle of redline water wetter to the anti freeze 50/50 mix.it works and drops the temp several degrees.
http://www.redlineoil.com/products_coolant.asp
ohlord