Cooling issues

[Coug]

My suggestion at this point is to open up the manual TM-9-2320-20-1 to page 2-164 and follow the flow chart diagnostics all the way, performing every single test that it tells you to without skipping any of them. Don't make any assumptions that just because you replaced a part that it "must be good" or anything else.
Follow EVERY single step, and record every result to review.


Or you can just keep buying more parts and throwing more money at the truck, hoping that something finally changes in what's going on and that you manage to get the correct part, or that something randomly changes for a bit and that the issue doesn't come back.


Not trying to be rude, but you've already done a lot of work on it, and already taken care of all of the commonly replaced items, so I'm just thinking it might be time to go back to the beginning and make sure you haven't missed anything.


If you aren't familiar with the manuals or how to use them, feel free to ask and we can help walk you though some of the more confusing aspects of military technical manual usage. (the PDF manual has links so you can jump from one troubleshooting item to the next one for your issue without having to flip pages, as it does skip about 10 pages at one point)

 

[Thumper580]

I’m sure it has been engaged since I got the truck 2.5 years ago. I bet that’s why I only get 7mpg also and other people talk about getting 10-12


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I had a similar problem with my 998. I checked and replaced all the parts and pieces leading up to the can clutch, hoping I wouldn't have to pull the radiator stack.....it ended up being the fan clutch..... Worked great after that and all the other pieces were "new". You did a great job at tracking it down.

 

[Dpas1973]

My suggestion at this point is to open up the manual TM-9-2320-20-1 to page 2-164 and follow the flow chart diagnostics all the way, performing every single test that it tells you to without skipping any of them. Don't make any assumptions that just because you replaced a part that it "must be good" or anything else.
Follow EVERY single step, and record every result to review.


Or you can just keep buying more parts and throwing more money at the truck, hoping that something finally changes in what's going on and that you manage to get the correct part, or that something randomly changes for a bit and that the issue doesn't come back.


Not trying to be rude, but you've already done a lot of work on it, and already taken care of all of the commonly replaced items, so I'm just thinking it might be time to go back to the beginning and make sure you haven't missed anything.


If you aren't familiar with the manuals or how to use them, feel free to ask and we can help walk you though some of the more confusing aspects of military technical manual usage. (the PDF manual has links so you can jump from one troubleshooting item to the next one for your issue without having to flip pages, as it does skip about 10 pages at one point)

Did you read my last reply? The fan clutch disengages with 120psi from my compressor nothing less. The Tm says the Cadillac valve operates from 30-90 psi I’m assuming my clutch is stuck that’s why it won’t disengage without 30psi over what the Tm states? Am I correct?


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[Coug]

Did you read my last reply? The fan clutch disengages with 120psi from my compressor nothing less. The Tm says the Cadillac valve operates from 30-90 psi I’m assuming my clutch is stuck that’s why it won’t disengage without 30psi over what the Tm states? Am I correct?


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Yes, I've read every post in this thread.
It does jump around a bit to be honest, and with everything going on, it seems that each of the individual pieces of the system pass when tested individually, but that overall the system still doesn't appear to function properly.

At nowhere that I read did I see that a comprehensive, step by step diagnostic was performed on the system, only that nothing changed as items were replaced.

My advice of starting from the beginning is because I've seen more than a few times when troubleshooting systems (not just HMMWV but all sorts of repairs) where someone decided to skip some of the diagnostic steps and wound up doing unnecessary expensive repairs only to have the equipment still not work until a very cheap/easy to fix item got replaced/repaired.


Since the concern here seems to be that the clutch isn't getting enough pressure from the power steering system, why not go down to the local hardware store, buy a T fitting and a couple barbs that fit the line out of the cadillac valve, and a pressure gauge that reads up to 250 or so. Put it in line and see. If you have over 90 psi pressure, then the only reasonable thing left is the fan clutch. It will be a lot cheaper/faster to do this than to tear apart the cooling stack to get to the fan clutch (I think you have to take everything apart but not entirely sure?) and at the end you'll know for sure that is what is going on, instead of maybe not having enough pressure from the cadillac valve assembly (unlikely but still possible)

(just saying that if you don't have the tool to test the pressure on that line, it shouldn't be hard to make one)

 

[Dpas1973]

Yes, I've read every post in this thread.
It does jump around a bit to be honest, and with everything going on, it seems that each of the individual pieces of the system pass when tested individually, but that overall the system still doesn't appear to function properly.

At nowhere that I read did I see that a comprehensive, step by step diagnostic was performed on the system, only that nothing changed as items were replaced.

My advice of starting from the beginning is because I've seen more than a few times when troubleshooting systems (not just HMMWV but all sorts of repairs) where someone decided to skip some of the diagnostic steps and wound up doing unnecessary expensive repairs only to have the equipment still not work until a very cheap/easy to fix item got replaced/repaired.


Since the concern here seems to be that the clutch isn't getting enough pressure from the power steering system, why not go down to the local hardware store, buy a T fitting and a couple barbs that fit the line out of the cadillac valve, and a pressure gauge that reads up to 250 or so. Put it in line and see. If you have over 90 psi pressure, then the only reasonable thing left is the fan clutch. It will be a lot cheaper/faster to do this than to tear apart the cooling stack to get to the fan clutch (I think you have to take everything apart but not entirely sure?) and at the end you'll know for sure that is what is going on, instead of maybe not having enough pressure from the cadillac valve assembly (unlikely but still possible)

(just saying that if you don't have the tool to test the pressure on that line, it shouldn't be hard to make one)

Thank you for reading everything and giving your advice. I’m going to have to get the gauge but this hasn’t worked since I got the truck 2.5 years ago. I did waste money just replacing parts like an idiot. 2 Cadillac valves,time delay,hoses from Cadillac valve water crossover sensor lol and 3 thermostats. Several hundred in wasted parts. I’m not a mechanic and never considered hooking the compressor up and seeing at what psi does the fan disengage with the motor running until someone on here suggested it. I’m sure I’m screwed and the fan clutch is stocking needing 120psi to disengage instead of the 30-90psi the Tm calls for


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[Coug]

Thank you for reading everything and giving your advice. I’m going to have to get the gauge but this hasn’t worked since I got the truck 2.5 years ago. I did waste money just replacing parts like an idiot. 2 Cadillac valves,time delay,hoses from Cadillac valve water crossover sensor lol and 3 thermostats. Several hundred in wasted parts. I’m not a mechanic and never considered hooking the compressor up and seeing at what psi does the fan disengage with the motor running until someone on here suggested it. I’m sure I’m screwed and the fan clutch is stocking needing 120psi to disengage instead of the 30-90psi the Tm calls for


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on the plus side, most of the parts you replaced are ones that do fail from time to time, so having spare ones on the shelf doesn't hurt.
Also all things considered, it was relatively inexpensive at only a few hundred dollars, compared to the thousands that some people have thrown at issues with no change.

It's a learning experience. I just want you to be aware that for pretty much any possible issue with these trucks, the manual has detailed, step by step instructions on not only how to fix an issue, but how to properly diagnose it as well. Sometimes the steps can seem overboard when you "know" what the issue is (or more accurately when you THINK you know what the issue is) but starting from the beginning and working yourself through all of the steps usually comes out faster and cheaper in the long run.

 

[Dpas1973]

on the plus side, most of the parts you replaced are ones that do fail from time to time, so having spare ones on the shelf doesn't hurt.
Also all things considered, it was relatively inexpensive at only a few hundred dollars, compared to the thousands that some people have thrown at issues with no change.

It's a learning experience. I just want you to be aware that for pretty much any possible issue with these trucks, the manual has detailed, step by step instructions on not only how to fix an issue, but how to properly diagnose it as well. Sometimes the steps can seem overboard when you "know" what the issue is (or more accurately when you THINK you know what the issue is) but starting from the beginning and working yourself through all of the steps usually comes out faster and cheaper in the long run.

Ok I had a fuel pressure gauge in garage I hope it will work for the fan clutch pressure. The gauge maxes out at 100psi. when I hooked it up it bottomed out past 100psi on the gauge. Idk if the gauge isn’t the right one?

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[Coug]

that gauge should be more than enough. It doesn't care what the fluid is, just the pressure.

So at this point you have plenty of pressure going out of the valve, all that is left is a couple hoses and the fan clutch.

It's always possible that the issue is somehow a failed hose, but unlikely, so looks like time to rebuild the fan clutch.

 

[Dpas1973]

that gauge should be more than enough. It doesn't care what the fluid is, just the pressure.

So at this point you have plenty of pressure going out of the valve, all that is left is a couple hoses and the fan clutch.

It's always possible that the issue is somehow a failed hose, but unlikely, so looks like time to rebuild the fan clutch.

I replace the upper hose from valve to fan shroud. I can’t get inside to replace the hose with the quick connect. It’s a highway job to pull that radiator stack especially in your driveway with no garage lol.

 

[Milcommoguy]

In case I missed something... looks like good pressure, say 120 psi plus. OK , back to the air compressor and at 120 PSI. Engine OFF. Can you spin fan easily as in more or or less free wheels, little resistance ? Then remove air. What the result?

That's todays big test, CAMO

 

[Dpas1973]

In case I missed something... looks like good pressure, say 120 psi plus. OK , back to the air compressor and at 120 PSI. Engine OFF. Can you spin fan easily as in more or or less free wheels, little resistance ? Then remove air. What the result?

That's todays big test, CAMO

Yea with engine off and no less than 120psi on compressor I can spin by hand. When I start the truck and lock it at 1500rpm the fan ony disengages with 120psi from air compressor


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[Mogman]

120psi is 120psi air or fluid, and it looks like that gauge on the cadillac valve is making around 120psi
Likely one of the gauges is off, you need to set up using the same gauge for the air and fluid.
Still pretty strange for sure...

 

[Milcommoguy]

I'am not sure we are going in circles.

At IDLE on my rig... valve power on then off it is a noticeable effect that the fan moves a 1/4 inch. With clutch engaged a slight loading of engine and a hurricane of air flow when any connector in system is disconnected. THIS IS only on a COLD engine, not up to temperature. Looking for the A and B... effect.

With all the parts swapping... Start with a known 24 volts right off the batteries or closer to you the alternator positive to valve lead , the other a ground. Use your handy dandy clip leads that I always recommend and have handy. Eliminate all the electrical monkey motion down stream.

The 120 PSI hydraulic, 120 PSI air gets clutch moving ?? A new Cadillac valve ?? Direct power on and off (above) and see what gives. Should be a noticeable change even at idle.

That truck is JINKed. Chasing tails on this one, CAMO