Air leak, front emergency gladhand, no air at rear gladhands

[Oxyacetylene]

Looking for some ideas on what to check. Whenever the System Park is disengaged, air is venting (a lot of it) through the front emergency gladhand. I replaced the one way check valve mounted beneath it on the T fitting, but that didn't help. I have seen some info online talking about replacing the check valve in the gladhand....but does the gladhand itself actually have a check valve?

Also, the rear gladhands are not getting any air. With the Trailer air supply valve set to supply air, does the System Park have to be disengaged for them to work? Maybe if another valve, like the truck protection valve, is faulty it could cause both issues?

 

[porkysplace]

You should be able to trace the air system part through this TM m1078_TM 9-2320-365-24P.pdf
m1078_TM 9-2320-365-24P for the M1078 series trucks.
The rest of the TM's are here
M1078 TM's

 

[Oxyacetylene]

You should be able to trace the air system part through this TM m1078_TM 9-2320-365-24P.pdf
m1078_TM 9-2320-365-24P for the M1078 series trucks.
The rest of the TM's are here
M1078 TM's

Thanks I have been reading through those, but I don't see a troubleshooting item for this particular issue. The diagrams in that particular TM will be useful for sure. I think next I will check the truck protection valve. The emergency gladhand also had some small pieces of (plastic?) being blown out. That leads me to believe a valve somewhere may have failed or something and came apart.

 

[porkysplace]

Thanks I have been reading through those, but I don't see a troubleshooting item for this particular issue. I think next I will check the truck protection valve. The emergency gladhand also had some small pieces of (plastic?) being blown out. That leads me to believe a valve somewhere may have failed or something and came apart.

Not being familiar with what valve is on it , does the parts book show any o-rings in the valve ? The plastic could be dried out o-rings from somewhere.
Edit : Have you serviced the air-drier yet?

 

[Oxyacetylene]

Not being familiar with what valve is on it , does the parts book show any o-rings in the valve ? The plastic could be dried out o-rings from somewhere.

Good point it could be dried out o-ring. I am still digging through the manuals to see where the different lines run and what valve is where. Thanks for the reminder to look in that manual, I had it, but didn't realize it had all of those diagrams. The other TM has some procedures for diagnosing various issues so if nothing else I can go through a few of those and it might reveal a bad valve or something.

 

[NDT]

The purpose of the front glad hand is so air from a towing vehicle can flow to the towed truck. The check valve prevents air from flowing when nothing is connected. I bet the check valve is cracked open by the plastic pcs you mentioned.

 

[Derrickl112]

.

 

[Tow4]

Is there a valve somewhere near the glad hand? My M929 has a valve right above the front emergency glad hand and if the valve is open and the glad hand cover is off, it will vent air.

 

[Oxyacetylene]

No such valve on these. I replaced the check valve last night and it didn't help. The check valve is on a T fitting, with one side going to the gladhand, one going through the check valve, and the third going inside to the System Park valve from what I can tell in the TM. It only dumps air while System Park is disengaged. The rear gladhands are actually working, or at least I verified the emergency one is working. The air coming through the front emergency gladhand has to be feeding in from the other line besides the one with the check valve. The System Park valve works as far as applying and releasing the spring brakes, but maybe it is still messed up?

 

[Tow4]

Try putting a cover on the glad hand or take it off and cap the pipe to see if the air pumps up and the system works normally. Maybe something is missing or installed wrong.

 

[Oxyacetylene]

Try putting a cover on the glad hand or take it off and cap the pipe to see if the air pumps up and the system works normally. Maybe something is missing or installed wrong.

Yep it definitely holds pressure when I cap that one off. I hooked up my air hose adapter to that gladhand and the system holds pressure.

 

[jtron79]

Did you solve this yet? Mine is leaking from the front and rear emergency gladhands. Going to work some oil in the tractor protection valve and the control body and see if that helps.

 

[Oxyacetylene]

Did you solve this yet? Mine is leaking from the front and rear emergency gladhands. Going to work some oil in the tractor protection valve and the control body and see if that helps.

Nope not yet. Next I guess I will try working backwards from the front emergency gladhand and see if a valve somewhere has malfunctioned. I called Haldex to ask a couple questions about the operation of the System Park and Trailer valves. The Delivery ports on the System Park valve are common/shared...basically if any air is back feeding on one of the delivery lines it could pass through the valve to the other delivery line. When I was telling them about the issue I am troubleshooting they said it sounded like a two way check valve somewhere might be bad. These trucks I believe have 4 two way check valves? I also got a couple part numbers to cross reference the System Park and Trailer valves in case you or anyone else needs to replace theirs.

 

[jtron79]

Defiantly post up the numbers! These should be serviceable and may just need an o ring replaced but you never know. I'll dive into the check valves first.

 

[Oxyacetylene]

The park valve can be replaced with KN20035 and the Trailer valve with KN20025. The newer trucks use a one piece manifold that contains both valves, and is serviceable. I took the bolts out of the plate holding the two valves, but there is not enough slack in the lines on mine to pull the valves out far enough to loosen any of the lines. I would need to either take the lines loose near the floor pan, or take out the heater assembly.

 

[jtron79]

I removed my Trailer supply valve first, it only has one line going to the floor all the rest feed off the other valve, it's tight but not that bad, you can hold the fitting with one wrench and loosen the nut and make great progress. It's full of gunk but the o rings look ok. can't figure out how to fully disassemble the entire valve to check the rest of it out. I also can't believe it's made out of plastic did they mention what model of combined valve the newer trucks used? If I replace them both i'd rather go with the combined style.

 

[Oxyacetylene]

I didn't ask about that one specifically, but I think they could help you pick one. They were very helpful when I called. If I have to replace mine at any point, I would be interested in the one piece one too. It would be easy to service those, it looks like the top plate just comes off so you can get to the internals.

 

[jtron79]

I replaced my trailer control valve as that is what was causing my air at rear glad hand. I started tracing the lines back from the front glad hand and i think they had this problem while it was in service because the check valve at the T is new. It functions correctly so i moved on to the the other side of the T which goes to a two way check under the drivers side, only accessible with the cab tilted. it's the valve at the top of the pic below. removed it and sure enough the rubber diaphragm is broken. the valve number is KN25060, it is used multiple places, but because the rest of the valve is in good shape i'll order up some repair kits. RN11V both items are stocked by NAPA. hope this helps a little.

 

[Oxyacetylene]

That is good to know. Glad you found the source of your problem. When I have some more time, maybe this weekend, I will try checking that on mine too. Thanks!

 

[tennmogger]

Great thread! I picked up an M-1078 today and had an air leak develop in the front emergency circuit while underway. AARP (card) to the rescue. This is the only good use I have found for a membership demanded by insurance requirements, saying no more.

This quick fix got me home with no further trouble.

The troubleshooting already done here should lead me to the fix, complete with part numbers!! Thanks,

Bob