All 6 tires airing down

[BiggDaddy]

1990 M925A2 New to me truck about a week ago. Seller told me CTIS worked but doesn't appear to. First the Hwy button blinks and then all the buttons blink but haven't had any issues until yesterday I got to work and all the tires were low. Manually aired all to 65psi. On my way home there was clicking and air solenoid type noises around the winch control tower. Noticed tires were airing down again while on the road. Got home and tires were very low, Heard air leak under dash coming from what looks like a small dryer? Has one red hose going out the firewall and under truck, and a Green hose that goes into the winch tower (may curve around somewhere else) Does anyone know what this is? It's leaking from the bottom hole and I thought a cap was missing but there is paint on the threads so doesn't look to have had anything on it. I'll take it apart today after work to investigate further. Thanks!

 

[DeMilitarized]

1990 M925A2 New to me truck about a week ago. Seller told me CTIS worked but doesn't appear to. First the Hwy button blinks and then all the buttons blink but haven't had any issues until yesterday I got to work and all the tires were low. Manually aired all to 65psi. On my way home there was clicking and air solenoid type noises around the winch control tower. Noticed tires were airing down again while on the road. Got home and tires were very low, Heard air leak under dash coming from what looks like a small dryer? Has one red hose going out the firewall and under truck, and a Green hose that goes into the winch tower (may curve around somewhere else) Does anyone know what this is? It's leaking from the bottom hole and I thought a cap was missing but there is paint on the threads so doesn't look to have had anything on it. I'll take it apart today after work to investigate further. Thanks!
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Its a main supply line for air to the ctis I belive. Mine started leaking so I plugged the hole. If you have 4 lights flashing on the controller simply hit runflat mode and it will bypass the fault. If all 5 are flashing there is an electrical problem in the system. If there are 5 lights solid the ecu is junk.

 

[BiggDaddy]

Its a main supply line for air to the ctis I belive. Mine started leaking so I plugged the hole. If you have 4 lights flashing on the controller simply hit runflat mode and it will bypass the fault. If all 5 are flashing there is an electrical problem in the system. If there are 5 lights solid the ecu is junk.

10-4 Thanks, I'll take it apart tonight when I get home and check it out further. I believe mine has 4 lights flashing. I pushed both red buttons to reset the system from something I read but they just blinked for a while and nothing happened. I also read the system needs 120psi to activate but mine is a little under. Was going to bump up my pressure on the governor to see if that helps but may read the troubleshooting manuals that were recommended first.
I know one thing, I feel bad for any soldiers trying to get out of harms way and the system starts dumping the air from all the tires!

 

[cbrTodd]

The thing leaking air is the filter on the inlet side of the CTIS. I couldn't get mine to stop leaking either. You can get a small air tool filter to replace it.

If the controller just blinks 1 highway light when you start the truck, that is the normal behavior. It should try to inflate to highway once the air tanks are full and the tank pressure switch closes. If that switch doesn't close, you can try adjusting the air governor up a few psi to see if it will. I had to bump my truck up to 125 psi a couple years after I got it, but that has worked for years since then.

If the pressure switch does close and you get 5 flashing lights, that is supposed to indicate a large leak in the system. Leaks are hard to find without some extra work since the lines are only pressurized for a short time before the PCU shuts it off. Take the cover off the solenoid box on the floor, find the outlet hose from the system, and hook up a constant shop air source regulated to 70 psi. Then go looking for any leaks without the truck running. You might find some in the hoses and fittings or around the outside of the wheel valves. You might hear noises inside the hubs indicating hub seal issues.

Let us know what you find and report back so we can advise further!

 

[Andyrv6av8r]

1990 M925A2 New to me truck about a week ago. Seller told me CTIS worked but doesn't appear to. First the Hwy button blinks and then all the buttons blink but haven't had any issues until yesterday I got to work and all the tires were low. Manually aired all to 65psi. On my way home there was clicking and air solenoid type noises around the winch control tower. Noticed tires were airing down again while on the road. Got home and tires were very low, Heard air leak under dash coming from what looks like a small dryer? Has one red hose going out the firewall and under truck, and a Green hose that goes into the winch tower (may curve around somewhere else) Does anyone know what this is? It's leaking from the bottom hole and I thought a cap was missing but there is paint on the threads so doesn't look to have had anything on it. I'll take it apart today after work to investigate further. Thanks!
View attachment 894124
View attachment 894123

A wheel valve core threaded in mine perfectly to stop a leak.

 

[KN6KXR]

Stop.

Unplug the CTIS module to prevent problems on the road until you get it working. Air up manually until you get it fixed.

You've lost a hub seal. At least one. Make a test tool like the one in the TM. Unplug the lines to the wheels one at a time and test them. I've got a dollar that says at least one hub seal is done for. Mine had 4. Same behavior as your truck. CTIS module was fine. The hub seals aren't expensive but the job is a PITA.

The water separator under the dash is the CTIS supply and has an auto drain that is pretty crappy. As posted here a standard tire schraeder can go in there you have to remove the auto drain if you want it right then remember to push it once in awhile and manually drain it. One of these days I'll put in a better water separator. It's on the list....

Lots of threads and posts on this. Sometimes Google searches this site better than the site itself does. Do both. Get the TM's for the system, the Dana CTIS manual and the P2P simulation program (all free downloads). That will help you A LOT. I really like my CTIS and actually use it. It took a lot of work to get it right but I think it's great.

 

[BiggDaddy]

As everyone said it is just an air filter. We have tons of these at the plant, just not that small. Had some corrosion so I cleaned it up with scotch brite, lubed the seal and orings and it works good now. If it acts up again I'll replace it or put in a schrader valve.

After that leak was fixed, I bumped up the pressure on the governor one turn which put me at 130psi (Will lower to about 125) The CTIS finally started working and aired all the tires back up. This is the first time the HWY light stayed on solid since I got her. This evening when I get home I'll drive it and start testing the hub seals.

 

[KN6KXR]

There's a pressure switch on the wet tank for the CTIS. I think it's on about 120 and off at 90. On mine it's located on a cross fitting. You can jumper this for testing.

When the hub seals go bad they might still work depending on the position they are in and how bad they leak. I never had luck tracking them until I got a shop supply run to the truck at 120 psi and made the test tool. With the truck running it's too noisy to hear exactly where it is. Also the hubs are so big it's tough feel the air escaping around the drum.

The test tool I made is a male connector that attached to the wheel supply line. Disconnect the line from under the truck, plug the test tool into the line, swing out so you can add air. I forget the exact test pressure. Since mine was a wrecker (90 psi) I tested at that. If it holds for 10 minutes it'll hold for an hour.

Be advised the fittings for front and rear may be different. Mine had JIC on the rear 4 wheels and SAE on the front two. I double checked the parts in the -34P and that is how they built them. Stupid, huh? I changed them all to JIC my local hose shop had all the fittings.

I carry my test tool with the truck and it's capped with a JIC cap to protect the threads. If a hub seal fails I can use the tool to locate and install the cap and run with 5/6 tires operational on the system. Luck favors the prepared.

 

[BiggDaddy]

There's a pressure switch on the wet tank for the CTIS. I think it's on about 120 and off at 90. On mine it's located on a cross fitting. You can jumper this for testing.

When the hub seals go bad they might still work depending on the position they are in and how bad they leak. I never had luck tracking them until I got a shop supply run to the truck at 120 psi and made the test tool. With the truck running it's too noisy to hear exactly where it is. Also the hubs are so big it's tough feel the air escaping around the drum.

The test tool I made is a male connector that attached to the wheel supply line. Disconnect the line from under the truck, plug the test tool into the line, swing out so you can add air. I forget the exact test pressure. Since mine was a wrecker (90 psi) I tested at that. If it holds for 10 minutes it'll hold for an hour.

Be advised the fittings for front and rear may be different. Mine had JIC on the rear 4 wheels and SAE on the front two. I double checked the parts in the -34P and that is how they built them. Stupid, huh? I changed them all to JIC my local hose shop had all the fittings.

I carry my test tool with the truck and it's capped with a JIC cap to protect the threads. If a hub seal fails I can use the tool to locate and install the cap and run with 5/6 tires operational on the system. Luck favors the prepared.

You're right about that! It's like sticking your head out of an airplane trying to hear an air leak.

 

[Jbulach]

With your system now “working” air down to emergency then while filling back up to hwy, start with a heavy soap solution in a spray bottle on the wheel valves, connections, and associated plumbing. There are a lot of different leak prone problem areas on these systems as well as the hub seals. The QR valve up in the frame rail can also get debris in them causing the diaphragm to leak while inflating.

 

[Jbulach]

Also, use shop air connected to the the red glad hand with engine off, in the run position if available. If no shop air, pull the hand throttle all the way out while airing up and checking for bubbles.

 

[BiggDaddy]

I finally found the leak today. With the truck parked there were no leaks but while driving you could hear a bad leak that would stop when I stopped the truck. Today when It started leaking, I pulled over and it was coming from the left middle tire where the valve is attached to the hub. After getting home I removed the bracket and the valve slid right off the tubing coming out of the hub (brass compression nut was loose) Cleaned the threads on the valve and brass nut, reinstalled the valve onto the hub, and reinstalled the bracket and no more leak. Test drove the truck and the CTIS finally seems to be working right! I'm calling that luck that it was an easy and free fix!
Thanks everyone for the help and suggestions! Picture is after I got it back together.

 

[Jbulach]

Same cause as one of my leaks, actually made some new seals out of heater hose to allow for a better grip.

 

[cbrTodd]

Glad to see things are going in the right direction for you!

I found a couple ideas on here for things that can help with the reliability of those seals if needed. One was to cut the brass nut down by a thread or two in order to allow it to clamp down harder on the existing seal. Basically give it a little more compression before the nut bottoms out. The other was to add a bolt and 2 nuts to the shield that goes behind the rear wheel valves, with the bolt arranged so that the head pushes radially against the inside of the wheel when installed. Then even if the brass nut does work loose, the valve can't slip outboard and come off that aluminum fitting. I did it to all my rear wheels after having a wheel valve come loose on the way to work one day. Let me know if you want pictures, I can get them but am not by the truck currently.

 

[BiggDaddy]

Same cause as one of my leaks, actually made some new seals out of heater hose to allow for a better grip.

That was my thought as soon as I got it off was I'm going to have to find some hose to make new rubbers but they were still in good shape, luckily just loose.

 

[BiggDaddy]

Glad to see things are going in the right direction for you!

I found a couple ideas on here for things that can help with the reliability of those seals if needed. One was to cut the brass nut down by a thread or two in order to allow it to clamp down harder on the existing seal. Basically give it a little more compression before the nut bottoms out. The other was to add a bolt and 2 nuts to the shield that goes behind the rear wheel valves, with the bolt arranged so that the head pushes radially against the inside of the wheel when installed. Then even if the brass nut does work loose, the valve can't slip outboard and come off that aluminum fitting. I did it to all my rear wheels after having a wheel valve come loose on the way to work one day. Let me know if you want pictures, I can get them but am not by the truck currently.

That's a good idea, I was wondering what I could wedge in there to hold it on temperately if it didn't tighten up. Luckily it did. I do need to pull all of the shields off to bead blast and paint them, it would be easy to add some bolts to them while they are off. Possibly weld a nut to the shield to be able to adjust the bolt. Thanks!