M1097 6.5L 4 speed Thermostat - fan - issue question....

[4x4nutz]

1996 M1097 runs great (we had previously flushed the radiator, added new coolant, and replaced the coolant temp sending unit), but after driving for just three miles (in 50 degree weather), fan came on and then did not shut off for the rest of the 7 mile trip. Later that day we ran it again and after a few miles the fan came on and did not shut off. Is it possible the thermostat is staying open? Also, does anyone have a generic part number for a thermostat and gasket as I want to replace the 25 years old one that's in it. FYI - I tried the TM, but just could not put everything together in my head. Thanx for reading.

 

[Retiredwarhorses]

First off, what was the indicated temp?
your issue is most likely a bad thermostatic switch, if you bought a Chinese knock off, I almost guarantee it.
to many folks replacing thermostats for absolutely no reason

 

[4x4nutz]

First off, what was the indicated temp?
your issue is most likely a bad thermostatic switch, if you bought a Chinese knock off, I almost guarantee it.
to many folks replacing thermostats for absolutely no reason

Engine temp 195 to 205. The coolant sending unit came off one of my other humvees...not chinese. We have not replaced the thermostat. We were inquiring about whether or not a stuck open thermostat would cause the clutch fan to remain on, and then we were asking about part numbers for a replacement thermostat if the thermostat needs to be replaced. If a stuck open thermostat causes the fan clutch to stay engaged, we will know it's not the thermostatic switch. All we use is OEM Mil spec parts.

 

[Mogman]

Engine temp 195 to 205. The coolant sending unit came off one of my other humvees...not chinese. We have not replaced the thermostat. We were inquiring about whether or not a stuck open thermostat would cause the clutch fan to remain on, and then we were asking about part numbers for a replacement thermostat if the thermostat needs to be replaced. If a stuck open thermostat causes the fan clutch to stay engaged, we will know it's not the thermostatic switch. All we use is OEM Mil spec parts.

I do not see how a thermostat being stuck open could be your problem, your indicated temp is normal

 

[Autonomy_Lost]

FYI there is one coolant sensor for your gauge, and a different one to control the fan. They are not the same.

 

[Mogman]

And a third one for the cold advance.

 

[4x4nutz]

FYI there is one coolant sensor for your gauge, and a different one to control the fan. They are not the same.

I understand that.

I do not see how a thermostat being stuck open could be your problem, your indicated temp is normal

That's what I was asking. Moving on to the thremostatic switch now that controls the fan clutch as per RETIREDWARHORSE.Thank you.

 

[Retiredwarhorses]

I understand that.

That's what I was asking. Moving on to the thremostatic switch now that controls the fan clutch as per RETIREDWARHORSE.Thank you.

Its a combination of parts in the cooling system, thermostatic switch, TDM, cadillac valve solenoid can all cause this issue, the cold advance has no bearing on any of this, thats just a switch for power to C.A. solenoid.

 

[4x4nutz]

Its a combination of parts in the cooling system, thermostatic switch, TDM, cadillac valve solenoid can all cause this issue, the cold advance has no bearing on any of this, thats just a switch for power to C.A. solenoid.

Which should I start with...time delay module? Attempting to complete this humvee by Monday for Warrior's Heart in Bandera.

 

[papakb]

With the engine running so the power steering pump is making pressure connect and disconnect the 2 wire connector to the Cadillac valve and watch the fan clutch move in and out about a quarter inch. If this happens the valve is working. Now do the same thing with the 4 wire connector. You should see the same thing happen. The fan temp sensor is on the top of the engine near the crossover manifold. This is the one that talks to the TDR and cycles the fan clutch. Leave the sensor on the side of the block behind the alternator alone. That's for the temp gauge only and has nothing to do with the fan. The one you want has 2 wires coming out of it. To test the fan sensor disconnect it and with a meter on resistance scale see if it shows a change as the engine gets hot and then another change as the engine cools down. Or just replace the darn thing with a new one. They aren't that expensive

 

[4x4nutz]

With the engine running so the power steering pump is making pressure connect and disconnect the 2 wire connector to the Cadillac valve and watch the fan clutch move in and out about a quarter inch. If this happens the valve is working. Now do the same thing with the 4 wire connector. You should see the same thing happen. The fan temp sensor is on the top of the engine near the crossover manifold. This is the one that talks to the TDR and cycles the fan clutch. Leave the sensor on the side of the block behind the alternator alone. That's for the temp gauge only and has nothing to do with the fan. The one you want has 2 wires coming out of it. To test the fan sensor disconnect it and with a meter on resistance scale see if it shows a change as the engine gets hot and then another change as the engine cools down. Or just replace the darn thing with a new one. They aren't that expensive

Dude ...your like a brain scientist! Thank you!

 

[4x4nutz]

Replaced the TDM. At this point, the temp comes up to around 195 while regular driving in just about 5 minutes from cold (driving between 20 and 55MPH) and the fan comes on. It stays on and temp climbs to around 215 and does not go any higher. Fan seems to keep temp from rising any further, but does not make the temp go down. First of all, why is the coolant temp coming up so fast to begin with I wonder? Replacing the thermostatic switch next. I appreciate y'alls help and I am relating what you say with the TM as I am a hands on learner and most of the time the TM just confuses me. Still learning at 62.

 

[Mogman]

Coming up to temp in 4-5 miles is pretty normal for my Detroit.

 

[4x4nutz]

Replaced thermostatic switch...old one looks questionable. Will test her out once the wife leaves for the liquor store...lol

 

[Retiredwarhorses]

even The US Military ended up with thousands of Chinese thermostatic switchs…Dave at HOG did a lot of investigating and worked with AMG, here is his notice on the switch.

IMPORTANT PART NOTE:
EFFECTIVE 10-2021 ANYTHING BUT "REM MFG" IS AFTERMARKET AND IS WORTHLESS POS AND DOES NOT OPEN OR CLOSE AT THE CORRECT TEMPS. AM GENERAL OBSOLETED THE SENDER IN 2015 AND STOPPED PROPERLY SOURCING IT WHEN THE HUMVEE WENT TO THE GEARED FAN DRIVE FOR COOLING..TLDR...SO EVEN THE AMG SOURCED ONES ARE INCORRECT - THEY DO NOT SOURCE FROM REM DO NOT TRUST EVEN AMG SUPPLIED SENDING UNITS - WE TESTED THEM AND THEY FAILED TOO. ONLY THE "REM BRANDED" ONES OPEN AND CLOSE AT THE PROPER TEMPS.

 

[4x4nutz]

even The US Military ended up with thousands of Chinese thermostatic switchs…Dave at HOG did a lot of investigating and worked with AMG, here is his notice on the switch.

IMPORTANT PART NOTE:
EFFECTIVE 10-2021 ANYTHING BUT "REM MFG" IS AFTERMARKET AND IS WORTHLESS POS AND DOES NOT OPEN OR CLOSE AT THE CORRECT TEMPS. AM GENERAL OBSOLETED THE SENDER IN 2015 AND STOPPED PROPERLY SOURCING IT WHEN THE HUMVEE WENT TO THE GEARED FAN DRIVE FOR COOLING..TLDR...SO EVEN THE AMG SOURCED ONES ARE INCORRECT - THEY DO NOT SOURCE FROM REM DO NOT TRUST EVEN AMG SUPPLIED SENDING UNITS - WE TESTED THEM AND THEY FAILED TOO. ONLY THE "REM BRANDED" ONES OPEN AND CLOSE AT THE PROPER TEMPS.

Way ahead of you...lol

 

[Autonomy_Lost]

even The US Military ended up with thousands of Chinese thermostatic switchs…Dave at HOG did a lot of investigating and worked with AMG, here is his notice on the switch.

IMPORTANT PART NOTE:
EFFECTIVE 10-2021 ANYTHING BUT "REM MFG" IS AFTERMARKET AND IS WORTHLESS POS AND DOES NOT OPEN OR CLOSE AT THE CORRECT TEMPS. AM GENERAL OBSOLETED THE SENDER IN 2015 AND STOPPED PROPERLY SOURCING IT WHEN THE HUMVEE WENT TO THE GEARED FAN DRIVE FOR COOLING..TLDR...SO EVEN THE AMG SOURCED ONES ARE INCORRECT - THEY DO NOT SOURCE FROM REM DO NOT TRUST EVEN AMG SUPPLIED SENDING UNITS - WE TESTED THEM AND THEY FAILED TOO. ONLY THE "REM BRANDED" ONES OPEN AND CLOSE AT THE PROPER TEMPS.

Interesting. Do you know anything about the Interlog Corporation TDM's? I have one with a Jan 2022 date, sourced from Mac Motors.

Edit: nevermind, were not talking about the same part

 

[4x4nutz]

So after replacing the thermostatic switch, after driving 3 miles the temp went all the way up to 240+ with fan on? The coolant reservoir cap vented a bunch of coolant and I am back to square one...the humvee is overheating for some other reasons other than the switch, caddilac valve, and TDM.

 

[Autonomy_Lost]

Try to narrow it down to coolant flow or air flow. Thermostat stuck closed or partially closed? Radiator clogged internally? Or dirty externally, inhibiting airflow? Just spitballing.

 

[Mogman]

One thing to check is if you have the correct fan, make sure it is not blowing forward, next I would try a thermostat, then having the radiator cleaned.
And as Autonomy suggested try and look between the cooler and radiator and see if there is any debris in there.