nbone28

It vents at 130psi

Yes the problem only occurs when I am connected to the trailer, disconnect the airlines from the trailer and no issue. There’s no issue with the truck. When I come in the next morning the air pressure is usually sitting at 55psi in the secondary tank and a bit more i’d say like 65-70psi in the primary tank.

Okay so where do I start then?

I had separated the trailer from the truck and tested it that way. From the initial posting I said when I go push in the trailer air supply that is when the leak is happening. I’d assume the trailer is the problem just from that. I’m answering all the questions that are being asked. The MV-3 was $200 and took about 5 mins to swap out. Not too worried about that. It looked like it needed to be replaced anyways.

I will test it tomorrow and report back!

Will check in the morning, 140 sounds about right.

believe it’s 160, i’ll have to double check in the morning

That’s with the tanks full, I let the tanks fill up and on the initial release they drop to 80psi.

Where do I start with the trailer? I don’t hear any air leaks coming from the trailer.

I do, they just don’t live anywhere “close” by where I park my truck.

I had the red line connected to my airline setup to air up the tires. It was not hooked up to the trailer. When it was connected to this I was able to push the trailer air supply in and it would stay pushed in. When I went back to it hooked up to the trailer the button will not stay pushed in.

I’ve tested it without the airlines hooked up to the trailer, there’s no leaking when you go to push in the trailer air supply and when you go to release it. When I hook it back to the trailer and test it, that is when the air is leaking out of that yellow airline. The problem has to be with the trailer. It’s a flatbed trailer that’s got a lift axle on it. That MV-3 valve was going bad either way it seemed like. Ended up being $211 for a new one.

Yes both tanks fall to 80PSI. I put in the new valve, hooked up the airlines, went to go test it out and the initial drop after pushing in the trailer air supply was 90psi in both tanks. After releasing the brake the air was leaking out that yellow airline still. Went to go test it again and the valve won’t stay pushed in. I unhooked the emergency line from the trailer and hooked it up to my airline to air up the tires and had no problem with the button staying pushed in when hooked to that. I go back to hook it up to the trailer and it won’t stay pushed in. It doesn’t leak when pushing in the yellow button by itself. The only recent work was the foot pedal valve, that I replaced about two months ago.

Replaced the valve & its still doing it. Air pissing out of that yellow line coming out of the fire wall underneath the hood and now the trailer air supply button won’t stay in to supply the air

Yellow Line is hooked up underneath the orange line on the left

Tracing that line now, will let you know

Emergency line hooked up still, service line off the trailer, no air coming out the service line.

Yes I hear air leaking out that yellow line until it drops to 80 psi, once it rebuilds back up the air doesn’t leak anymore

When you go to push in the trailer supply you hear the air pissing out from that yellow line outside the firewall. The psi drops to 80 and then will build back up. It holds air perfectly fine after the initial drop. It’ll then piss out air once you go to release that valve.

I pull the same trailer everyday. I stay hooked to it. It isn’t leaking constantly out that yellow line, when you go to push the red button in, air leaks out of that yellow line, the air will drop to 80psi in both tanks, and then build back up. Once it builds back up it doesn’t leak again until releasing the trailer brakes.

Changed the brake valve out a little over 2 months ago, this just started happening on Monday.

Trucks over in the New Haven area. It’s only occurring when engaging and releasing the air supply to the trailer. I’m not losing air when I go to brake.

2015 Mack Pinnacle cxu613, when I go to push in the air supply for the trailer (and when i release it) air is pissing out from underneath my hood. I’m not losing air when I go to brake, it’s only when I go to engage or disengage to air supply for the trailer. It’s pissing out of the top yellow airline in the photo. It looks like there is a valve behind the firewall, could that be what’s causing this? Thanks for the input.

2015 mack pinnacle cxu613 mp8, oil leaking behind the side bolt on the oil pan. Passenger side. Is there an o ring behind that bolt on the inside of the pan? Any insight would be appreciated. Thanks

The top one or bottom one of those two sensors?