emilybecker1

M Klasse Overheating and Slow Warm Up

My 2001 Mercedes M Klasse with a gasoline engine is overheating at 281071 km. It's also slow to warm up. Could a bad thermostat cause this? I think it might be a map thermostat, but I want to be sure before spending 350€ on a repair. Coolant level is fine, and I don't see any leaks. Could it be the water pump instead?

4 comment(s)

Sounds familiar. I had similar overheating problems with my old Opel, different brand, different engine. Long warm-up times too. Is the thermostat housing showing any signs of leakage? It could be the thermostat but also, maybe, just maybe, a sensor giving the wrong readings.

The thermostat housing looks okay, no leaks. The coolant system seems to be holding pressure. You mentioned a sensor issue. Was that the cause of your overheating?

In my case, the sensor was a red herring. Eventually, it turned out to be the thermostat like I initially suspected. If you aren't totally confident, maybe get a professional opinion. Could save you some hassle in the long run.

Thanks. I appreciate the insight. I'll take it to a trusted mechanic for a diagnostic. If it is indeed the thermostat, I will have it replaced.

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