300e thermostat
 

how do you replace the thermostat on a 300e. I know you remove the thermostat cover then do you just lift it up and replace it with the new one. Is there any special sequence in installing it. Also can changing it cause air to get trapped in the cooling system.

Hey I know this one!
 

I had to replace the leaky plastic thermostat cover on my '86 300E with a new aluminum one. The new cover contains a a bolt on top that acts as a bleeder valve. (search for breeder valve) The thermostat just pulls straight up and out, and the new one slides right in. Leave the bolt out of the aluminum cover while you fill the radiator.

--Craig

The stat has a small vent value. Make sure it is at the highest position (it is not level).

You can also a thin film of oil on the gasket.

You never mentioned what year of engine type you own, but as far as installing the thermostat at the highest position in the housing, it's not all that obvious for some models.

The housing is nearly level on the 3.2 M104 engine configuration, but if you check verrrrry closely, you can see a slight dip near the back of the housing.

You will be 99% correct if you have the little vent hole pointing toward the windshield, which, if you are looking directly above the housing from the front grille, is at about the 12 o'clock position...