My friends 300D has an overheating problem in the Summer months. So far he has changed out the water pump, radiator, and two thermostats. My thought was he should check the fan clutch. Any other suggestions?

The MB crank driven fan is prone to failure at high mileage. I had to change 2 and I only have 100,000 miles on the clock.

The fan will still move but will not engage when it should and if you had the air-conditioning on you are in trouble.

This isn't your problem but it is a helpful additive to help cool your car, it's called diesel water wetter....lowers the temp of the operation from 5-10C. It's nice to leave your A/C on when your going through the Mojave Desert. Goodluck with your fix!

Thanks guys. I'll check the fan this weekend!

I recommend checking your fan clutch, and maybe checking out the diesel giant web site. I saw something about drilling holes on the side of your thermostate in order to let more water through so the car does not overheat.

What year??