GovPlanet Humvee Arrival and Inspection

[jake20]

So in terms of my transfer case and the detent for the "H" position. As I stated earlier, it shifts into H fine, but it's very loose feeling. I removed the shift assembly to see if the detent was at the shifter or within the transfer case itself. I'm 99% sure it's the transfer case at this point.

My problem with this has been the fact that it pops out of "H" into "N" randomly when driving. I kept having to keep slight pressure on it with my thumb to keep it from moving.

So... here is my bandaid fix: I noticed the rubber boot that the shift levers slide into would put a good amount of pressure on the transfer case lever, so I cut notch in the boot to stop it from doing so. It has yet to drop out of "H" yet on me after doing so. This definitely isn't the permanent fix but it works for now

 

[jake20]

More infos!

So as I walk this path of endless maintenance, I decided to tackle my cooling system the other day. I'll report on some findings here in case some other soul stumbles across this during their cooling system endeavors.

Problem:

As I'm driving, the temp gauge would consistently get to 220F and the engine would operate at that temperature. It's on the hot side in my opinion, although I haven't verified with a laser temp gun (it's on the way). As far as I understand, you want it to be close to 200F for a diesel, so around 195-205 would calm me down inside.


Findings:

The first thing I did was completely flush everything out of the system (I think). I opened the drain valve at the bottom of the truck on the radiator line, and drained as much of the old garbage out as I could. I then started filling the system with a garden hose and repeatedly draining until I was getting clear water out of it. Then I did it some more. I had the heater running during this as well so as to flush that system somewhat too.

After doing this for about an hour, I drove around to watch the temps, aaaand they would stay the same, around 220F on the gauge.

So the next thing I did was check the coolant tank fittings/lines for obstructions. @Retiredwarhorses posted this somewhere at some point and I vaguely remembered what was written, so I did what I recalled reading. Remove the 2 small lines connecting to the plastic tank, and make sure the nipples are clear of obstructions. I did this and found some sort of silicone jammed in one of them. The next thing I checked was to blow through either of those lines, and hear air come out the other, both passed this check.

I then re-assembled the system, went for a drive, and the same results prevailed

So onwards with my troubleshooting. I figured it was possible that the thermostat was stuck closed after years of sitting. I removed the top radiator hose, and then the thermostat housing. Thermostat came out easy and didn't look corroded at all. It did however look nothing like the photos I have seen of 6.5L engine thermostats. I'll attach some pictures, but I have no idea what this one is. As far as I understand, the 6.5L engine thermostat has a little rubber circle on it and looks very different.

Anyway, I re-assembled the system without the thermostat, that way I could see what temp it gets to with maximum flow. Same results, but it took much longer to get to 220F, so I know it's not the thermostat (probably).

And my last effort - The Cadillac valve. I checked this last, because I thought my fan clutch was already stuck completely closed. Every time I have ran the truck, the fan has ran 100% of the time. What I did not realize, is that the clutch was only partially closed, and the fan was not running at its maximum speed at any point. I figured this out by disconnecting electrical power to the valve, and then suddenly seeing the fan ramp up to at least double the speed it was turning at.

With this new discovery, I took the truck for a drive with the valve's power disconnected. Success! The temp maximized around 185-190F the entire time. So at this point, I've at least got the problem narrowed down to what I think is a faulty fan clutch.

Plenty of pictures attached for the curious.

 

[Coug]

At any point did you use a laser thermometer to verify the temp gauge is accurate?

Fan doesn't engage until at least 220 on NA unit's and I think around 230 or 240 on turbo trucks.

With my cadillac valve unplugged, the truck sits at 180 degrees.

And yes, 220 degrees is still within normal operating temperature and won't cause any harm to your motor no matter how long it stays there.

As for "partially engaged" it's either all or nothing.
Yes, the fan does spin whenever the engine is on, but that's just fluid drag inside the clutch. You can reportedly stop it from spinning with just your hand, but I'm not willing to try that.

If your temp isn't hitting above 220 then the fan won't engage. Just keep an eye on it, and if it gets above 230 then you can worry, but you can calm down and relax that as far as you have stated, everything seems to be functioning properly so far.

And the temp gauge and sender are military spec, which ultimately means they are just for general reference, and not to be taken as absolute fact.

 

[springer1981]

And my last effort - The Cadillac valve. I checked this last, because I thought my fan clutch was already stuck completely closed. Every time I have ran the truck, the fan has ran 100% of the time. What I did not realize, is that the clutch was only partially closed, and the fan was not running at its maximum speed at any point. I figured this out by disconnecting electrical power to the valve, and then suddenly seeing the fan ramp up to at least double the speed it was turning at.

With this new discovery, I took the truck for a drive with the valve's power disconnected. Success! The temp maximized around 185-190F the entire time. So at this point, I've at least got the problem narrowed down to what I think is a faulty fan clutch.

I'm no expect but I can tell you my personal experience. From what you say it sounds like you expect the fan to stop turning when it is suppose to be disengaged? The fan always turns and in the disengaged mode it doesn't move very much air. When the clutch engages the fan kicks up a lot and more lots of air. Because you saw this happening when you disconnected the Cadillac value that indicated the fan clutch is working properly. Sounds like you have an electrical issue in the fan control circuit ie, temp switch, time delay switch etc. and the fan isn't engaging when it gets to a higher temps (over 220). Your temp gauge in the dash could be off too.

If you watch the fan clutch closely (the end with the hose going in) when you unplug and plug the Cadillac valve you will see it move in and out about 1/4" but you have to look closely.

 

[diesel_dave]

Sounds like there's nothing wrong with your cooling system to me. At least, it's exactly how my truck operates and it's been fine so far.

 

[jake20]

At any point did you use a laser thermometer to verify the temp gauge is accurate?

Fan doesn't engage until at least 220 on NA unit's and I think around 230 or 240 on turbo trucks.

With my cadillac valve unplugged, the truck sits at 180 degrees.

And yes, 220 degrees is still within normal operating temperature and won't cause any harm to your motor no matter how long it stays there.

As for "partially engaged" it's either all or nothing.
Yes, the fan does spin whenever the engine is on, but that's just fluid drag inside the clutch. You can reportedly stop it from spinning with just your hand, but I'm not willing to try that.

If your temp isn't hitting above 220 then the fan won't engage. Just keep an eye on it, and if it gets above 230 then you can worry, but you can calm down and relax that as far as you have stated, everything seems to be functioning properly so far.

And the temp gauge and sender are military spec, which ultimately means they are just for general reference, and not to be taken as absolute fact.

Hey @Coug thanks for the input! Yea I'm waiting for my laser temp gun to arrive, so I haven't been able to verify how accurate the gauge is yet. Thanks for confirming the clutch operation too, like I said, I'm not a mechanic, so I assumed that the fan wouldn't spin if the clutch was disengaged

Once I get the temp gun and a new thermostat, I'll report back with how things look. Thanks everyone!

 

[05blackduramax]

Unhook your two wire plug on the time delay module while its running, should engage your fan clutch.

 

[05blackduramax]

If you see the fan clutch hoses move and you dont see or hear the fan engage you can free up the fan clutch with a mallet.

 

[jake20]

If you see the fan clutch hoses move and you dont see or hear the fan engage you can free up the fan clutch with a mallet.

I may try this, very very slowly lol.

I've been slowly watching/listening for the engine's trends as I cruise around the block. Once I reach a hair past 220F on the gauge, the hydraulic hissing sound from the pump (I think) goes away, and you hear the fan ramp up to 100%. Then it drops slightly below 220F, and the hissing resumes while the fan spins down. So I guess mine likes to just sit at that 220 level, assuming that's what it actually is. I got the temp gun now, will be verifying actual numbers soon.

I haven't had any issues with coolant/water spraying out of the overflow either.

 

[INFChief]

I may try this, very very slowly lol.

I've been slowly watching/listening for the engine's trends as I cruise around the block. Once I reach a hair past 220F on the gauge, the hydraulic hissing sound from the pump (I think) goes away, and you hear the fan ramp up to 100%. Then it drops slightly below 220F, and the hissing resumes while the fan spins down. So I guess mine likes to just sit at that 220 level, assuming that's what it actually is. I got the temp gun now, will be verifying actual numbers soon.

I haven't had any issues with coolant/water spraying out of the overflow either.

Rarely has anything been resolved by playing whack-A-mole. I don’t beat on anything that I don’t want to destroy or that’s a solid chunk of something I’m trying to remove.

 

[jake20]

Rarely has anything been resolved by playing whack-A-mole. I don’t beat on anything that I don’t want to destroy or that’s a solid chunk of something I’m trying to remove.

Yea I'll verify my actual temp numbers first I suppose, and then re-install a thermostat.

 

[Coug]

I may try this, very very slowly lol.

I've been slowly watching/listening for the engine's trends as I cruise around the block. Once I reach a hair past 220F on the gauge, the hydraulic hissing sound from the pump (I think) goes away, and you hear the fan ramp up to 100%. Then it drops slightly below 220F, and the hissing resumes while the fan spins down. So I guess mine likes to just sit at that 220 level, assuming that's what it actually is. I got the temp gun now, will be verifying actual numbers soon.

I haven't had any issues with coolant/water spraying out of the overflow either.

That is exactly how the system is supposed to operate.

And once again, yes, these engines operate hotter than gasoline motors do, and 220 is perfectly normal. Still a good idea to verify with the laser thermometer just to understand the relation between your temp gauge and actual engine temps, but at this point you have nothing to worry about.

The hissing sound is usually from the cadillac valve. Some people wrap it in rubber from an old inner tube or similar to reduce the amount of noise.

As the sound goes away when the fan is engaging, it's functioning properly.

 

[jake20]

So I guess one of the main things I haven't found an answer for yet, there are 2 types of CDR valves based on my research.

One of them is cheaper, and has the two large diameter nipples

The other is more expensive, has the two large diameter nipples, and then also two smaller diameter nipples (I presume this one is for the deep fording setup)

My humvee doesn't have any valve, so it's basically spewing blow-by around the doghouse area. I'd like to put a valve in, but I'm wondering if it matters as to which one I put it. I don't plan on going through neck-high water.

My valve was somewhat roughly removed during the de-mil process. They cut the driver-side foot heater hose, the CDR bracket still remains on the engine block itself, and there are a few small tubes, along with the large tube coming from the oil filler, all in that general area. I think the smaller tubes are the vent lines that connect into the CDR, but I don't know if I need to worry about them or not. I've attached some pictures.

 

[Maxjeep1]

I didn’t want the water fording when I replaced mine on my M1123. I ended up changing my mind and realized that I might want to make it functional later on but I can’t use my CDR valve. I ordered the water fording valve for my M1165.

 

[jake20]

Looks like @Mogman has answered the CDR question for me in another post from April: https://www.steelsoldiers.com/threads/deep-water-fording-kit.209083/post-2440356

Suppose I'll do some searching for pricing and see what I want to go with.

 

[jake20]

Finally had a chance to verify with the temp gun up close to the thermostat housing. The housing was consistently 10-20F lower than what the gauge in the cab indicates. So when at 220F on the gauge, it'd be reading around 210 on the temp gun. Once the fan kicks in, it brings the temp down on the thermostat housing to about 195, but the gauge still sits at 215-220.

Sounds like my cooling system is in fact working properly, so the gauge is just all over the place. Starting to wonder if the needle on it can even go past 220 lol.

 

[911joeblow]

There could be a lot of trapped air at the back of the block. These engines are notorious for that. We have a kit to bleed that off and create a flow path to reduce the rear head/block temps the better balance the cooling system.

 

[Guyfang]

Yep! it was the hoses. Went to Napa and bought some temporary fuel line to replace it with, leaks are gone, woohoo.

Anything you do temporary, needs to be done again. Do it right one time, and be done with it.

 

[jake20]

Anything you do temporary, needs to be done again. Do it right one time, and be done with it.

Yep that’s absolutely right. Although I wanted to be able to pull it into the building I’m using to work on it, without making a huge mess under it.

I used fuel line of the same diameter as the original return lines, and they’re on pretty tight. My plan was to order the braided stuff, as I understand it’s supposed to be difficult to pull off. Not sure if the fuel line I used is acceptable as a substitute.

I’m waiting on a few factors and then I can yank my injector pump to be sent for a rebuild. I can swap the return lines again much easier at that point if anything.

 

[jake20]

There could be a lot of trapped air at the back of the block. These engines are notorious for that. We have a kit to bleed that off and create a flow path to reduce the rear head/block temps the better balance the cooling system.

I’ve actually read the write up on your site. I may consider it down the line once I’m driving it more often and can observe how the temps are acting.