The thermostat in my 93 idi turbo starts to slowly rise under load over a period of time or going up steep grades. Doesn't leak or loose coolant anywhere and I've already replaced the thermostat. Pretty sure the fan clutch is fine even though the fan is on at all times. Oil cooler has been rebuilt and doesn't leak from anywhere , theres no coolant in the oil so I'm kinda lost. Any new ideas would be awsome thanks.

 

if you did not use a motorcraft or international thermostat, remove the one you put in and replace it again with either a motorcraft or international thermostat. aftermarket units do not work in these engines and will most of the time cause an overheat condition.

 

Ok thanks for the heads up I'll have to look into it.