Mercedes ML Hybrid Overheating and Slow Warm Up

I had a similar issue with my Mercedes ML, though it's not a hybrid. The long warm-up time and overheating point towards the thermostat. It's like the thermostat is stuck closed, preventing proper coolant flow. Have you checked for any coolant leaks around the water pump or the radiator? A leak can sometimes cause similar symptoms.

Thanks for the insight. I haven't seen any coolant leaks, but I'll check the water pump and radiator more closely. If there are no leaks, is replacing the thermostat the next step to fix the cooling system?

If you're not seeing any coolant leaks, and the symptoms match, it is very likely the thermostat. Like a sticking door, it's preventing the coolant system from doing its job. However, I'd still recommend getting it properly diagnosed by a workshop before throwing parts at it. Replacing the thermostat might resolve the issue but a workshop can confirm it or maybe its something else entirely.

I appreciate the advice. I'll take the car to a workshop for a professional diagnosis of the cooling system. Thanks again for your help.