Today I was getting the 1992 7.3 ready to install in my 86 F350. I was changing the water pump and thermostat before I install it in the truck. I was cleaning the old gasket off of the thermostat housing (coolant outlet) and a steel ball the size of a BB fell out of I'm guessing is some type of bypass port. The gasket I was cleaning off of it totally covered it, so originally I didn't even know it was there. How important is this check ball? It was totally blocked off originally so could I hurt anything if I block it back? I checked with the Ford dealer and they didn't even show it in the parts diagram.

 

That check ball is supposed to be retained in the upper coolant manifold by either a plastic outer sleeve or a cork one. It is there to allow air to escape from the engine block during filling of coolant and normal driving.

Also only install the correct tstat, IH or Ford only no exceptions...
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

 

I sent a post to this question usually it goes to a moderator for ok first, because I list a different site for the pics I want you to see. Hang in there......

 

Since my check ball assembly fell apart and doesn't seem serviceable, could I just block off the bypass port in the block with the new gasket and install the t-stat I have since it does have a bypass in it?

 

The oem tstat does not have a bypass in it. i would try and run it with out the ball in it. But you will overheat with any off the shelf tstat. use only a Motorcraft tstat

 

Thanks for the information. I forgot I had another t-stat housing on the 6.9 sitting right beside the 7.3. They look virtually identical except for a couple of very small differences. This one does have the check ball and everything intact. I am going to go buy a motorcraft stat though. Thanks again.

 

i have gone thru two t-stats in the last 6 months. both have stuck in the open position. neither were motorcraft. i need a new t-stat now, so i will go buy a motorcraft.

thanks for this posting.