M931A2 trailer brake air problem

Picked up a M322 trailer and hooked up the glad hands with the truck not running. The primary and secondary air gauges showed 110 psi but very little air flow was coming out of the emergency glad hand. Started the truck and then had a lot of flow. The trailer air system has a few very small leaks.

While driving the air gauges showed 110-120 psi but the dryer would blow off every 5 min. Seems like somehow a check valve isnt allowing air to the trailer air system.

I have an XM1061E1 trailer. I found that the glad hands on the trailer were reversed, left to right.

In the box on the tounge it will have red and blue lines to show which are which.

Your trailer brake glad hands only get air from the wet tank. Nothing else. Your primary and secondary tanks on the truck have check valves so they can not back feed to assist with trailer air up. The wet tank on your 5 ton is half as big as what's on the m322. Your gauges should not reflect any air loss to the trailer

There is no check valve between your wet tank and the rear or front glad hands. There is no check valve on the trailer either.

You had a rush of air at the glad hand with the truck running cause the compressor is it's only support of air

Plus make sure the spring brake release on the trailer tounge is not engsged

Your dryer is blowing off due to your wet tank dropping down on pressure and then getting back to.max pressure. Your governor reads air thru the pressure protection valve which is off the wet tank. So even though your other gauges are not dropping your wet tank is and it is blowing off due to that tank getting to pressure repeatedly. May have a trailer leak

On my XM1061E1 trailer, the glad hands were colored red and blue, but were colored opposite the way they should have been.

glcaines said:

On my XM1061E1 trailer, the glad hands were colored red and blue, but were colored opposite the way they should have been.

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Those are air over hydraulic on a 1061 . With the m322 being full air s cam brakes If the brakes are not caged it wont roll without air.

Thanks Wes that's exactly what I was looking for. Sounds like the only thing I need to do is fix the air leaks on the trailer.

MAdams said:

Thanks Wes that's exactly what I was looking for. Sounds like the only thing I need to do is fix the air leaks on the trailer.

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Yes with trailer air leaks even minimal it can take 10 to 15 mins for the wet tank to charge the trailer tank and its lines. It would help yo add another air tank to the truck that would supplement it. Cause that trailer does eat some air when braking. especially loaded. Make sure the ABS works as well while you are back there. Uses the same control module as the m939 series trucks on it. with no weight the brakes will lock up pretty quickly.

MAdams said:

Thanks Wes that's exactly what I was looking for. Sounds like the only thing I need to do is fix the air leaks on the trailer.

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Easiest way to deal with the air tank and air brake valve area is to remove the floor. Getting up inside that little area between the axle is a real nightmare. Plus some of the lines can only be accessed from the top on the end of the tanks. Trailer takes type 30/30 long stroke brake chambers if you need to replace them.

Awesome. Thanks again. Now I need to look into finding smaller tires. 295/75 22.5 are still too tall and hit the outer frame. How do you haul a 5 ton and not be over 14ft tall? 255/70/22.5 might work

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MAdams said:

Awesome. Thanks again. Now I need to look into finding smaller tires. 295/75 22.5 are still too tall and hit the outer frame. How do you haul a 5 ton and not be over 14ft tall? 255/70/22.5 might work

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Your truck will squat almost 5 inches on the tongue due to the weight. Flatten the tires. The rear of the trailer still sits high but it's fine. I ran 385 65 22.5s. Which were alright. I went to dual 275 70 22.5s for the weight capacity. Dropped me 5 inches. You can also cut the wheel well humps off and you will gain 3 inches in the rear. Since truck tires sit on top of those.

Remember. the smaller the tires the heavier the trailer Is to pull plus you feel all kinda bumps. It's a heavy trailer as it is but I can really feel it with 275s on it back there. I have looked into adding a lift axle to get rid of some tounge weight.