Ok, I just changed the coolant and installed a temp gauge this weekend and now I have a new question. My truck never gets hot , the most i've ever seen is "o" on the "normal" scale. Now that i have added a graduated gauge i can see that i am only getting about 50'c (120'f). Today i removed the top hose and there is a thermostat in the housing. My question is can they stick open and let the coolant return to the radiator too soon? If so i will replace as soon as i can. The twit at the parts shop said to replace it with a falcon one as they are the same size and open temp (192'f) but are not the double acting one as we do not get freezing temps over here. 34'f is our min and not very often. Winter now and days around 70'f and nights around 40'f. Does this sound like a reasonable thing as the oem motorcraft part is about $100 over here. I think I can get one from RockAuto for around $40 with freight which i will do if its the way to go.

 

i would say the thermostat is stuck open.i have an thermostat from autozone in mine.it has worked fine for 2 years so you might be ok with the thermostat from rock auto.i have ordered many parts from them over time and have never had an issue.also my truck never gets hot unless its got a good load on it.i just have the factory gauge and it usually rides on the "n"

 

Do you have International trucks over there?

Best thermostat to use is either stock Ford or an International thermostat.

No bypass in the stock thermostat.
And many have posted problems using aftermarket thermostats.

There is one that a couple people have used with good results, Stant something I think, but I don't remember what.

 

The one from RockAuto is still a motorcraft one so thats ok. I consulted the manual lastnight and it turns out the double acting has nothing to do with freezing but actually means that when it opens it closes a bypass passage so that the water has to go to the radiator. It has two sealing faces hence double acting. I think I will order one this week.

 

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