My 1990 7.3 has been overheating under a load, pulling a mountain empty or pulling a load. I have changed the clutch fan, hoses and the thermostat and no change. What is left the water pump and the radiator? Anything else?

 

did you use a ford or international thermostat, or an auto parts store thermostat??. the 7.3 will not work with anything but a ford or international t-stat.

 

Did you clean the little ball check valve next to the thermostat in the thermostat housing? If it is fouled then you could be getting vapour lock as it is there to relieve any steam, vapour, air to the radiator.

Are you still running the 1990 radiator. If so it probably is getting pretty plugged up and need a new core.

Best of luck,
Seb....

 

Yep, an auto parts t-stat, but it was like $30+.

No I didn't check the check ball and it still has the 1990 radiator.

 

well, unfortunately, price makes no difference. i have never seen an auto parts store t-stat that worked in a navistar diesel.

 

I had the same problem with my 1992. I changed everything fanclutch radiator thermostate still would run hot under a load or in the hills it turned out to be that little ball in the check valve. that is in the termostate housing. I replaced the the housing and the problem whent away. you can get the themostat housing from rockauto.com for under $30 and a ford factory thermostat from the same place for under $25. delivard.

 

Hamberger & gabyski, thank you very much, That's the kind of advice I'm looking for. I will give that a try. I'd never thought there was a check ball in the T-housing. I'll let you know if it works.

 

The Five things to consider when you got overheating problems on the 7.3l are:

1, Fan Clutch / waterpump
2, Radiator
3, Thermostat
4, Air Vent Check Valve sticking.
5, Cylinder Wall Cavitation.


Best of luck,

Seb.....