i have a 1982 300d turbo-diesel that runs hot when im hammering the car on the highway or climbing steep hills the temp. gauge is almost in the red zone, but has never overheated
when i let off on the gas, the temp. gauge goes down.
i replaced the water pump a few years ago, replaced the clutch fan last year, and supposedly the thermostat was replaced a few months ago ,the car does not leak any anti-freeze.
i cant figgure out whats wrong.....any ideas ?

Search threads for head gasket and cracked heads and then read the many to see if your symptoms are similar, could be that under heavy engine loading conditions that combustion gasses are forced into coolant. This may be a longshot but more than a few threads that start like yours, end like this. Good luck!

maybe, but im not getting any oil in my anti-freeze or visa versa