M1078 LMTV Fix-up Thread

[CallMeColt]

After talking with someone via PM a bit, I tried to remove the line from the controller under the dashboard when the wheel valves were stuck open & check for some leaking air that maybe was getting past the valves inside... nothing. Passenger side wheel valves stick open still.

I made a fitting to connect the line going to the wheels directly to my compressor hose. The passenger side wheel valves stay open doing it that way as well.
Strangely but not surprising, the rear quick release valve stopped leaking when filling.

I replaced the front quick release valve just because I had one & wasn't sure the front one was good. Same results.

I still think I am having some sort of air pressure keeping those valves open in the line. The only thing I have no done was rebuild the drivers side wheel valves. Going to try that tomorrow. Not sure what else to do.

 

[M1078MAN]

You are help others more then you can imagine, even ones with experience.

Thank you for documenting

 

[CallMeColt]

You are help others more then you can imagine, even ones with experience.

Thank you for documenting

I just hope that I can get it figured out!

Once I do, I plan to make an entire video on the CTIS for my YouTube. How it works, parts of the system, & troubleshooting.

 

[coachgeo]

I just hope that I can get it figured out!

Once I do, I plan to make an entire video on the CTIS for my YouTube. How it works, parts of the system, & troubleshooting.

1. don't assume the truck is plumbed correctly. Not the first.... nor will it be last to find plumbed wrong.
2. Sounds also like leaking valve (switch or check orr?) somewhere letting low pressure air by....... just enough to open the dump valves a tid bit.

 

[Third From Texas]

Are you sure that the new controller is compatible?

I read somewhere that you can't put an A1R controller on a A0 truck.

You don't have a modified psi sensor installed (the poor man's higher psi controller mod).

 

[CallMeColt]

1. don't assume the truck is plumbed correctly. Not the first.... nor will it be last to find plumbed wrong.
2. Sounds also like leaking valve (switch or check orr?) somewhere letting low pressure air by....... just enough to open the dump valves a tid bit.

I have traced every single line from the compressor to the wheels to confirm they are clear by blowing them out individually. I doubt that anything is plumbed incorrectly because the system tries to do what it is supposed too. It will fill & deflate the tires. If it did not do that, I would think it was a plumbing issue.

Somewhere, some air is keeping the valves open. It has to be that. My best guess right now is one of the non-rebuilt wheel valves closes slowly & it is causing the other ones to stay open. Once I can get all the valves back on & rebuilt, I will be able to test this theory.

 

[CallMeColt]

Are you sure that the new controller is compatible?

I read somewhere that you can't put an A1R controller on a A0 truck.

You don't have a modified psi sensor installed (the poor man's higher psi controller mod).

It is a new, green controller. It was sold as a new controller only for A0 trucks.

No modified sensor installed that I know of.

 

[Plasa]

There shoud be a line between PCU and front bumper. It's used to depres the entire system quickly and is connection the the control valve of the PCU. Got a truck where that line was not free and system was not depressed fast enough.

Initially I had a ECU from a 6x6 with higher pressures. One wheel valve did not close due the higher pressure and was always leaking...

Christian

I have traced every single line from the compressor to the wheels to confirm they are clear by blowing them out individually. I doubt that anything is plumbed incorrectly because the system tries to do what it is supposed too. It will fill & deflate the tires. If it did not do that, I would think it was a plumbing issue.

Somewhere, some air is keeping the valves open. It has to be that. My best guess right now is one of the non-rebuilt wheel valves closes slowly & it is causing the other ones to stay open. Once I can get all the valves back on & rebuilt, I will be able to test this theory.

 

[CallMeColt]

There shoud be a line between PCU and front bumper. It's used to depres the entire system quickly and is connection the the control valve of the PCU. Got a truck where that line was not free and system was not depressed fast enough.

Initially I had a ECU from a 6x6 with higher pressures. One wheel valve did not close due the higher pressure and was always leaking...

Christian

Yes, made sure this was clean as well.

 

[CallMeColt]

Removed the drivers side wheel valves to rebuild them. Even with PB Blaster, heat, and care, I still broke 3 of the 8 screws holding the wheel valves together. My friend took them to his machine shop to drill out & tap the holes. All fixed.

Before I got them back, I had one spare valve. I rebuilt that one & put it on the rear drivers side. I removed the rear passenger & put it on the driver side front to see if the issue happened with a different valve. I put a plug in the stud on the wheel missing it's valve. I did notice one of the hoses from the wheel stud to the valve was a bit kinked on the front one so I changed it. I also found the connection at the front axle hub on the drivers side to be a little loose so I snugged it up.

When filling, the rear quick release valve would stay open as if it was dumping a little causing the controller to go into RUN FLAT mode. All the wheel valves would close when the controller was shut off. Strange. I did not expect that to happen with the quick release valve. I believe the kink hose I replaced was causing the opposite side front wheel valve to stay open since that problem is now gone.

Once I got the wheel valves back, I installed it after rebuilding it. Filled the truck with air, tested it & it started checking & filling. Once it was done & purged, the passenger rear wheel valve stuck open. Back to the original problem after all this! One time, after about ten seconds, before I could manually push it close it did close itself.

I took the fill port off the rear differential to see if pressure was in there that may be getting by bad CTIS seals. Didn't notice any.

What else could be holding air in the rear axle area to keep that passenger wheel valve open? As I said above, I blow tested everything individually & the valve will close that way. I'm completely at a loss & really bummed about this! Any more ideas?

For now, I filled the tires to 80PSI & took the breaker out of the panel. If I keep doing the same stuff over & over looking for the gremlin in there, I'm going to hate this truck.

 

[Plasa]

There are 2 types of wheel valves, for 4x4 and for 6x6. They have diffrent part numbers and max pressure. But the QRV should be the same on all LMTV models. What happen if you don't use the hwy mode, but the xc mode? Is the system more stable than?

Christian

Removed the drivers side wheel valves to rebuild them. Even with PB Blaster, heat, and care, I still broke 3 of the 8 screws holding the wheel valves together. My friend took them to his machine shop to drill out & tap the holes. All fixed.

Before I got them back, I had one spare valve. I rebuilt that one & put it on the rear drivers side. I removed the rear passenger & put it on the driver side front to see if the issue happened with a different valve. I put a plug in the stud on the wheel missing it's valve. I did notice one of the hoses from the wheel stud to the valve was a bit kinked on the front one so I changed it. I also found the connection at the front axle hub on the drivers side to be a little loose so I snugged it up.

When filling, the rear quick release valve would stay open as if it was dumping a little causing the controller to go into RUN FLAT mode. All the wheel valves would close when the controller was shut off. Strange. I did not expect that to happen with the quick release valve. I believe the kink hose I replaced was causing the opposite side front wheel valve to stay open since that problem is now gone.

Once I got the wheel valves back, I installed it after rebuilding it. Filled the truck with air, tested it & it started checking & filling. Once it was done & purged, the passenger rear wheel valve stuck open. Back to the original problem after all this! One time, after about ten seconds, before I could manually push it close it did close itself.

I took the fill port off the rear differential to see if pressure was in there that may be getting by bad CTIS seals. Didn't notice any.

What else could be holding air in the rear axle area to keep that passenger wheel valve open? As I said above, I blow tested everything individually & the valve will close that way. I'm completely at a loss & really bummed about this! Any more ideas?

For now, I filled the tires to 80PSI & took the breaker out of the panel. If I keep doing the same stuff over & over looking for the gremlin in there, I'm going to hate this truck.

 

[CallMeColt]

There are 2 types of wheel valves, for 4x4 and for 6x6. They have diffrent part numbers and max pressure. But the QRV should be the same on all LMTV models. What happen if you don't use the hwy mode, but the xc mode? Is the system more stable than?

Christian

I did try the XC mode before with no different result but I may try it again just to see.

I didn't know of there being two different part numbers. Though, there have been 3 different wheel valves on that passenger rear & all have had the same issue so I'm thinking it is not a wheel valve issue.

 

[CallMeColt]

Finally made the video showing my tire changes.

 

[CallMeColt]

After letting the truck sit for a bit, I tried again.

I tried XC mode & the wheel valve sealed up after about 5 seconds of staying open.

I have determined that the problem is between the passenger rear lug port & the port that is behind the wheel.

I used one of the nuts off the spare that holds the banjo bolt on to seal the banjo bolt tight on the passenger rear wheel valve. Blowing air into it with a blow gun, it opens & seals perfectly as it should.

Next, I removed the hose from the fitting behind the wheel valve & blew air in. The wheel valve stays open! I re-attached the wheel valve obviously.
If I plug the lug port, the CTIS works fine. Perfectly actually.

I did also check to make sure no air was getting into the axle via a bad CTIS seal in the hubs.

I'm attaching a picture of a hub.

Where the green arrows are pointing to I bet I have a minor obstruction. I'm going to have to pull my hub off & remove this line to clean it. May also have buildup in the hub area as well. I plan to do a full axle service as it makes sense to do it all at once. So, it will be a long while before I can post an update on this issue but it HAS to be it.

I will follow up though!

 

[CallMeColt]

So, I decided to tackle another issue on the truck. Major fix complete!

 

[CallMeColt]

 

[Third From Texas]

Did I miss who did the shaft balancing?

 

[Third From Texas]

I have a set that needs balance and a single (rear) that needs a total rebuild.

Looking at options to get it done. We *used* to have several local driveshaft shops, but they are long gone. The places that I've contacted all farm it out. I need to reach out to SA or HOU I suspect.

 

[CallMeColt]

Did I miss who did the shaft balancing?

I didn't think it would matter in the video so I didn't say. It was the old Driveshafts Unlimited in San Antonio, TX. They were bought out by INT Truck Parts.

 

[CallMeColt]

I have a set that needs balance and a single (rear) that needs a total rebuild.

Looking at options to get it done. We *used* to have several local driveshaft shops, but they are long gone. The places that I've contacted all farm it out. I need to reach out to SA or HOU I suspect.

I sent you a message directly with the information to the place I went!