Mercedes-Benz W202 does not reach normal temperature – thermostat
Mercedes-Benz W202 does not reach normal temperature – what is the most common cause?
The most common cause is a thermostat stuck open: the temperature stays at about 50–60 degrees and does not rise. Replacing the thermostat usually normalises the temperatures. On CDI models the small thermostat can also be the cause, and in winter the diesel's small amount of waste heat emphasises the fault.
Where are the Mercedes-Benz W202 thermostats?
The main thermostat is at the end of the upper coolant hose, where a thinner hose from the expansion tank also connects. The small thermostat is only on CDI diesels, not on petrol engines. A replacement part does not always match the original, so check the connections before installing.
How do I check the operation of the Mercedes-Benz W202 thermostat?
Once the engine has warmed up, the upper coolant hose should be warm and the lower hose cooler. The thin hose from the thermostat to the expansion tank also warms up only after the thermostat has opened. If the upper hose stays cold, the fault is in the coolant circulation.
What is the normal operating temperature of the Mercedes-Benz W202?
The temperature gauge typically shows about 80 degrees in winter and slightly over in summer. On some cars the value is higher. The thermostat's stated temperature is the point at which it is fully open, and it is rarely reached. The main thing is that the thermostat does not open too early.