M1078 Flat front tire with no help from CTIS

[7212]

I have a M1078 with a drivers front flat tire. The CTIS is no help. I can air the tire up through the valve using an air compressor but it wont hold air overnight. When I hit the HWY CTIS button, it flashes, cycles then remains lit without airing the tire up. All the other tires are holding air. Where to start? Would it help to cycle through a sand or snow cycle then back to HWY? Thanks for the help

 

[simp5782]

Bad wheel valve more than likely.

Remove the line from the stud to ensure you have air there when the ctis is operating. If so then a wheel valve is the culprit. Unless you have a leak before that somewhere on the truck.

Member suprman has some for sale in the classifieds

 

[Ronmar]

Yep, sounds like a wheel valve. I remove the banjo bolt on the large hose connected to the wheel stud like Simp5782 suggested, but I tape a rubber glove over the hose back to the wheel valve. If the glove inflates the wheel valve is leaking. If so, Deflate the tire and remove the 4 screws on the wheel valve and remove the cover. It has a spring and rubber diaphragm inside and may just have crap where it seals the small center hole that goes to the tire. One of mine was doing this and a good cleaning fixed it.

A really leaky tire might fault CTIS as will a tire that is radically different in pressure from the rest, but you may also have leaks elsewhere in the system. Once the wet tank is to full pressure the first thing the system does is close the control solenoid and give a shot of air with the supply solenoid to pressurize the system and open the wheel valves. Then it looks for a stable air pressure at the pressure sensor. A leak or low tire will cause an unstable pressure until the tires equalize and will fault the system.

Leaks are easier to find if you feed the truck shop air to the front emergency gladhand(chock the wheels as this releases the park brake) and can leave the engine off. It is easier still if you can remove the connector at the controller and jumper the pins on the cable end connector to energize the control solenoid and briefly energize the supply solenoid to pressurize the CTIS system. This allows you to leave the system pressurized as long as necessary to throughly look for leaks instead of waiting for the controller to briefly pressurize the system till it faults and you must reset it...

 

[Coffey1]

Before it does it's first cycle test hit run flat.

 

[coachgeo]

interesting how majority of the ctis leaks are driver front

 

[7212]

UPDATE

No air through the big hose at all while truck is running and all tanks are full. Also the air tanks do not leak down overnight. Its almost as if this tire CTIS is capped off somewhere for this wheel. I cycled the CTIS through the sand setting and 3 tires deflated and then at the end of the cycle I hit HWY and 3 inflated. No action on this tire at all. I did air it up manually and it deflated within 30 minutes. I hear no leaks in the tire area.

 

[simp5782]

UPDATE

No air through the big hose at all while truck is running and all tanks are full. Also the air tanks do not leak down overnight. Its almost as if this tire CTIS is capped off somewhere for this wheel. I cycled the CTIS through the sand setting and 3 tires deflated and then at the end of the cycle I hit HWY and 3 inflated. No action on this tire at all. I did air it up manually and it deflated within 30 minutes. I hear no leaks in the tire area.

Remove the ctis valve from the wheel and install a valve core in the valve stem for the wheel directly. air it up. See if it leaks down. IF no then you have a bad wheel valve for sure. If it does then get your soap bottle out but more than likely an O ring but if it leaks down in 30min then you have a pretty big hole somewhere.

 

[Ronmar]

Yea, thats a big leak.

the rubber glove works real well for seeing if the wheel valve is leaking past without having to remove and add a schrader valve...

the front quick release/dump valve for CTIS is on the right side of the transmission(inside the frame next to the fuel tank). It has one line in from CTIS(top line) and 2 lines out(front and rear) to each frame passthru and down to each axle end. The line to the drivers wheel is the line coming out of the valve toward the rear which loops around to the rear of the transmission and up along the drivers frame rail to the passthru fitting and down to the axle fitting...

 

[Andyrv6av8r]

I know someone who had the same problem recently on a fairly-new-to-him truck. After investigating, we found that wheel had a solid bolt from a 1082 trailer instead of the hollow banjo bolt in the airline and couldn't inflate.

 

[Coffey1]

Yea I forgot about that lol

 

[coachgeo]

I know someone who had the same problem recently on a fairly-new-to-him truck. After investigating, we found that wheel had a solid bolt from a 1082 trailer instead of the hollow banjo bolt in the airline and couldn't inflate.

how would that make it deflate though? Granted could be two different problems

 

[Ronmar]

how would that make it deflate though? Granted could be two different problems

Two different problems I think. Based on the way the QR/dump valves operate I dont think there is a way for a failure to isolate 1 wheel. A solid bolt where the banjo bolt should be at the wheel or I would suspect a line has been disconnected and plugged/capped to bypass a bad line or a blown hub seal...

 

[Andyrv6av8r]

how would that make it deflate though? Granted could be two different problems

This guy had a leaky tire that couldn't be filled because of the bolt; so yes 2 issues. After putting in a banjo bolt it worked fine.

 

[Coffey1]

Lol Andy you can say it was me I won't be offended.
Sometimes were dummies lol.

 

[coachgeo]

This guy had a leaky tire that couldn't be filled because of the bolt; so yes 2 issues. After putting in a banjo bolt it worked fine.

Confusing???. you say it was 2 issues...... then say only one thing fixed. So did one thing fix both?

if so curious how solid banjo created an air leak??? not sealed right?? cause if solid was an issue..... trailer tires would not hold air.

 

[Andyrv6av8r]

His tire didn't leak down as fast as the OP's. It would take a few days to go flat. The bolt wouldn't make it go flat.

 

[SausageGuy]

Mine had a solid bolt in one wheel as well.

 

[7212]

You guys nailed it. It has a solid bolt in it. I thought that was odd. It also had only 1 rubber washer on it. Found the other washer in the cab. I will be picking up another LMTV from Ft Campbell this week or next for a parts donor.

 

[7212]

Now that i've thought about this, the wheel is tan on a green vehicle. I'm betting the GI changed the tire and placed the correct bolt somewhere in the pattern.

 

[Coffey1]

That's why Andy is my Scotty lol.