My 300sd starts to run hot on the freeway, precisely the same as the guy a few posts ago “Diesel runs hot”. Should I expect a dramatic loss of power when it begin to get hot? It behaves as though it is firing on 4/5 cylinders…a few seconds it runs good, then followed by crappy. Could this be boost coming in and out? I just replaced injectors, fuel filters, and cleaned with Diesel Purge. Also, when it acts up, the shifting just goes all to hell. When I drive it around town, it shifts perfect and has awesome power. Also, when it gets hot, around 115-120, my glow plug dash lamp flickers and even turn on. I’m assuming this is telling me I’m overheating?

I appreciate your help!

 

I assume it is pre 85 model?
It is very likely 10 years past due on radiator replacement.
Don't think those models had any overheating lights indicators, but I am not much of electronics specialist.

 

I think I had that post. Well, the problem is now fixed. Actually I initially thought I had a coolant blockage, but it was not that. Mercedes dealership said the fan clutch was not functioning and replaced it. It is now working just beautifully, and the car is noticably cooler when running.

Most people say that if the car is running on the highway, the fan clutch shouldn't matter, but for me it did matter and it was the problem. Now it is fine.