ishboo

So recently my check engine light showed up on my 2007 Mercedes Benz e350. The OBD 2 reader gave a code of p0128 - which refers to the coolant thermostat in the car. So I checked for any leaks (no leaks), checked the coolant level (perfect level), and checked on how long it takes the car to warm up from a cold start (did this 2 days in a row). The gauge inside the car says the engine is at 80 C, which is how much the engine was every day I drove the car before the light as well. It takes about 5 minutes to get to this temperature from a cold start. The car isn't overheating and the car seems to be accurate from the gauge and time it takes the engine to warm up (I tried turning the heater on as well to see if warm heat was coming out and once reached to 80 C, it was releasing warm heat like always). After doing some research, I am still confused on what it could be - the thermostat or a sensor? ALSO, I deleted the code today from my OBD 2 reader and drove it around for about 10 miles and the check engine light hasn't come back on. Here are my questions:

Should I worry about the code if it doesn't come back? If it doesn't come back, would it have just been a faulty code error?
If I need to fix it or the code comes back, Is it the thermostat or a sensor?
If it's the sensor, which one is it? (I believe there are 3 total is this car)

Thanks!

mtrevelino

If you are still running the original thermostat, I would change it. The sensor should be included in the thermostats housing. The normal operating temperature is 90 C, at least that is what it is on my cdi.
Mike T.

ishboo

Sounds good! Just checked the thermostat with a live data scan and found out it is the thermostat

Thanks @mtrevelino

cetialpha5

The thermostat is well known to go all the time. Get the Wahler from Amazon, this one is cheaper because they misspelled it. Wahler is the MB OEM. You may also want to get the drive belt kit from Rockauto while you're at it because you have to take the pulley off to get at the thermostat. The tensioner is also known to go.


http://www.rockauto.com/en/moreinfo....434587&jsn=407

Looser

2009 W211 E350
I have the same problem, changed the Thermostat and housing complete.
Same problem P0128 code and Check Engine still on.
was it an air bubble form the beginning. or is it an air bubble now .
the Stat I removed was fine and now possible bad sensor ?
but same problem. any suggestions ?