Ran my humvee to 235 degrees and didn't hear the fan clutch engage. I parked to let it cool down and tested the fan clutch, Cadillac valve and temperature switch and they all tested good, the Cadillac valve was at 67 ohms, I didn't hear the fan clutch kick in after 220, would a bad thermostat cause this?
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Humvee running hot
- Thread starter jim1131
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First things first, get a laser thermometer or other method of verifying the engine temp. Don't trust the gauge to be accurate.
Not the thermostat. The fan would kick in, and unless you're at an idle, you'll hear the fan kick in.
If it's that hot, unplug the cadillac valve. If it engages then there is an issue with the wiring, a sensor, or (what failed on mine) the Time Delay Module.
If it doesn't engage then it's the cadillac valve or the fan clutch.
You can unplug when cold and the cadillac valve should engage the fan clutch.
Not the thermostat. The fan would kick in, and unless you're at an idle, you'll hear the fan kick in.
If it's that hot, unplug the cadillac valve. If it engages then there is an issue with the wiring, a sensor, or (what failed on mine) the Time Delay Module.
If it doesn't engage then it's the cadillac valve or the fan clutch.
You can unplug when cold and the cadillac valve should engage the fan clutch.
I unplugged the temperature sensor to keep the fan engaged but it still didn't cool down, I think I should try taking out the thermostat I'm hoping it's the cause of this problem I'm not looking forward to replacing the radiator.
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When you unplugged the temp sensor, did the fan engage?
If not unplug the cadillac valve itself. If the TDM (Time Delay Module) fails, it will keep the fan disengaged no matter what the senders are doing.
If not unplug the cadillac valve itself. If the TDM (Time Delay Module) fails, it will keep the fan disengaged no matter what the senders are doing.
Action
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Are the radiator hoses hot?
Is the gap between radiator and oil cooler clogged up with leaves and junk?
Is the gap between radiator and oil cooler clogged up with leaves and junk?
No, hose isn't hot and nothing is clogged up, actually the top radiator hose didn't have much pressure when I sqeezed it. I disconnected the temp switch wires and the fan clutch stayed engaged but it didn't cool down and the temperature reached 240 before I parked and let it cool down. I'm hoping it's a bad thermostat, I don't want to buy a new radiator
The fan did engage but the temperature stayed hot and reached 240
blutow
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If radiator isn't hot and the engine is really 240, it's likely the thermostat or I guess it could be some major obstruction if you have junk in the cooling system. How are you determining that the engine is hitting 240? If using the gauge, that's likely not a real reading. My guage is off by about 20 degrees compared to taking a reading at the temp sensor (it actually reads low, not high, but you get the point).
Action
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The fan pulls are thru the radiator fins to cool the coolant. Your fan system can be perfect, but if the hot coolant isnt flowing thru the radiator, it wont cool down.
FWIW, the fan always spins, even when not engaged.
FWIW, the fan always spins, even when not engaged.
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You should be able to tell if the fan is actually engaged at high RPM it will really roar, as others said make sure it is actually getting hot with a temp gun, the guages are notoriously inaccurate.
Do not just remove the thermostat, replace it if you think that is necessary but again do not run it without a thermostat and do not by a "cooler" one thinking it will help these engines need to run rather hot.
Usually when the thermostat is stuck it will get hot real fast and the cooling system will "thump" as the water boils in different parts of the engine.
Do not just remove the thermostat, replace it if you think that is necessary but again do not run it without a thermostat and do not by a "cooler" one thinking it will help these engines need to run rather hot.
Usually when the thermostat is stuck it will get hot real fast and the cooling system will "thump" as the water boils in different parts of the engine.
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Water pump can fail internally....
So the guage that came with the truck isn't accurate?
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built by lowest bidder...
They are electrical, and rely on resistances changing as temps change.
It is always a good idea, when trying to diagnose an issue you think you have because of a gauge reading, to verify the gauge is reading accurately. They can be off because of a bad sender, a bad gauge, a bad electrical connection, etc.
I recently had my oil pressure start reading erratically. Ended up being an issue with the sender leaking oil out through the electrical fitting.
The gauges mostly just give a rough idea of what's going on, and if what they are telling you changes, then start looking for issues. Obviously what it's reading for you has changed, so always a good idea to make sure you have an actual issue, and not just a bad gauge, before spending a lot of time and money fixing an issue that might not even exist.
So to reiterate, verify you have an issue, and do that by verifying that the gauge is reading properly by using a laser thermometer or similar device to check engine temp at the metal next to the thermostat and the sensor.
Will do, thank you for the help
papakb
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