Replacing a defective thermostat on your Mercedes is critical to keeping the engine running efficiently. If the thermostat is not working correctly, it can cause the engine to overheat, which can create further problems with the motor. The thermostat sits on the top of the engine near the front, next to the water pump, and is very simple to remove. Because it sits horizontally under the thermostat housing, draining the radiator to change the thermostat is not necessary. You can replace your Mercedes thermostat in about an hour.
Locate the thermostat housing that sits near the front of the engine next to the water pump. The housing has two water hoses that run into its underside from the radiator.
Detach the two bolts on the thermostat housing that are holding the cap in place with a metric socket wrench. When the bolts are removed, use a flat-edge screwdriver to lift the cap off the thermostat housing.
Lift the thermostat out of the housing and use a piece of emery cloth to clean any remaining gasket material or debris from the thermostat housing and cap.
Spread a layer of gasket seal around the edge of the thermostat housing and place the new thermostat on top of the housing.
Place the cap back on the thermostat housing and secure the bolts with a metric socket wrench. Take the cap off of the radiator and fill the coolant back to the proper level.
Start the engine and check the thermostat housing to verify that there are no leaks.
