How do I change the Thermostat in a 1984 Ford Diesel

 

Here is how on my 93 yours will have different accessories on that side, just remove what you need to get at the upper manifold bolts........

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 any 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 items in reverse order........

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

 

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I replaced my thermostat a couple of weeks ago. Pretty much followed the procedure that PLC laid out for you. It's pretty straightforward. Definitely pay attention to the little ball. It's gotta be able to move freely. My thermostat was stuck open, and the little ball was stuck as well. I sucked on the bottom of the housing and popped it free. (WARNING: Kids, don't do this at home! We're trained professionals!) Put it back together with a new (Ford) radiator cap and 8 gallons of coolant, and fired it up. I noticed that when I drove, the gauge would fluctuate a bit. Before the stat change, the needle stayed just below the operating range (cold). On the first trip after installing the new stat, the needle stayed in the lower end of the operating range. On my next trip (200 miles), it came up to just below midpoint. On the trip back home, it stayed at midpoint. Since then, it stays right around the midpoint, or just below. So don't be surprised if it takes a few miles for the system to 'normalize' and the gauge to read consistently.

 

Thank For The Info