I am new to the ford diesel world. I just bought a 84 with a 6.9 auto tranny. The truck is running hot so I put a new radiator in it and flushed the system with cooling system cleaner. The old coolant was nasty with muddy rust type stuff in it.
It is still running hot. The dash gauge reads at the top of the "normal" range. I checked the temp with a temp gun. I am getting 195 at the top of the radiator and 145 at the bottom of the radiator. Is this normal? Should I replace the thermostat? It is a pain to get to it so I dont want to change it if I dont have to.
Where is the check valve and could this be my problem?
Any info would help
Thanks

 

Diesel engine coolant temperature at the top of the radiator where hose attaches after high rpm or under load condition for 20 minutes should be (195-237*F) 91-114*C nice time to have a temperature reading point and shoot tool.

If the rad and cooling system was that nasty do the thermostat.......

CAUTION:
The specified/required thermostat does not contain an internal bypass, since the bypass is located in the cylinder block. Whenever the thermostat is replaced, it is mandatory that only Motorcraft E5TZ-8575-C or Navistar 1807974C94 thermostat be installed.

CAUTION:
Do not attempt to repair any thermostat. It should be replaced if it is not operating properly.

Check the new thermostat before installing it for correct opening temperature. Before suspending in boiling water, with a flashlight check where the rubber and the flat metal flange meet for bad seal. Tstat should start to opening barely at 180-192f, fully open 200-212f, allow to cool and check for rubber seal again.

Removal: Disconnect batteries, drain 4+ gals A/F, remove: as required, fan belt, alternator set aside, alt bracket, remove filter support from fuel filter then e/block. Disconnect upper rad hose at rad, remove tstat bolts and housing. Clean both faces, depression and holes in block, ensure check ball in goosekneck is clean, free and rattles "do not remove".
Installation is reverse proceedure, I do not use sealant on gaskets and faces. REMEMBER the tstat pellet(copper end) goes into the block. I do use a "very small amount" of sealant on the edge of the tstat face when installing into the recess, now go for coffee, allow sealant to setup, this has saved me from tstat slippage when the gasket and goosekneck are installed. Replace all items in reverse order......

Manifold bolt torque......... 20ftlbs

 

Wow

Thanks for that
I ran it at 60mph for 30 min and I was getting 195 at the top of the radiator.
Could my in dash temp gauge sending unit be reading too hot?
If so, where is it located so I can swap it out.

Thanks

 

There are two senders, the temperature guage sender is in front of the drivers head in the block, has a straight connector wire end. The second is the overheat sender it is on the lower front corner of the drivers side head, has a 90* connector. The overheat sender will activate at 244*F if memory serves me..... it will then peg the heat guage to "High" and illuminate the engine light.

 

Thanks again PLC7.3
Because we have been going back and forth and you are clearly "The Man" with info. I would be a fool not to ask you another question.
Again I am only 2 weeks old in my diesel life. I noticed I have a pump under my alternator which I can only assume is creating vaccume to my break booster. Here is my question... My breaks seem to work fine but they take a heavy leg to stop the truck. Could I not be getting enough vaccume out of the pump? or is it more likely that my booster diaphram is leaking?
Thanks again
Micah