HMMWV Overheat Q's and pictures

[Retiredwarhorses]

My ‘02 M1035A2 cycles just under 240, engages the fan and drops to 224, then rises to back to just below the 240 line. I verified the fan clutch to be operational. The TDM was disconnected when I received the truck from GovPlanet. I performed all the fluid and filter changes. I have driven about 500 miles with this, tried another temp gauge, replaced the sending unit and fan switch with Hummer Parts Guy parts, replaced the thermostat (HPG part), replaced the Cadillac Valve and TDM (no effect on the cooling cycle), flushed the Radiator three times, and replaced the lower metal coolant tube with a stainless steel one. I added WaterWetter to the coolant. I have a Gano Filter in the upper radiator hose that traps particulate and can be removed and cleaned (3 Xs so far with sludge and small rust chunks removed from the system) and after all this the temp range while driving remains unchanged. Ive read that these trucks routinely operate in the 220 to 20 range but would like o see it cycle at 225. What say you guys?

should never get past 220 before the fan engages…the thermostatic switch is likely the culprit, but have you actually verified this to be truly the temperature? Have you changed the radiator cap? have you verified you have built pressure when at operating temperature?

 

[Mstng65HummrMan]

should never get past 220 before the fan engages…the thermostatic switch is likely the culprit, but have you actually verified this to be truly the temperature? Have you changed the radiator cap? have you verified you have built pressure when at operating temperature?

I have a new radiator cap, i used a laser thermometer on the upper radiator hose that showed 71 cold then up to 193 at temp. I got readings on many different pat like engine block, lower radiator hose, crossover, etc, and non was over 200. I did buy a used temp gauge, installed it, and it read the same…

I have not verified pressure though, although I have released the overflow cap pressure to burp the system at operating temp in an effort to alleviate air from the system. It seem to make a difference with fluid level but not temperature indicated.

 

[Retiredwarhorses]

I have a new radiator cap, i used a laser thermometer on the upper radiator hose that showed 71 cold then up to 193 at temp. I got readings on many different pat like engine block, lower radiator hose, crossover, etc, and non was over 200. I did buy a used temp gauge, installed it, and it read the same…

I have not verified pressure though, although I have released the overflow cap pressure to burp the system at operating temp in an effort to alleviate air from the system. It seem to make a difference with fluid level but not temperature indicated.

if the upper radiator hose is hard, it’s pressurized.
i would run a wire direct from the engine temp sensor to the gauge…I’ve seen high resistance shorts cause erroneous readings.
just run it out side of the truck and plug into the gauge, just for a test.