Trailer backfeeding at Tractor protection valve when applying service brakes.

ok just let me when you find the bad brake chamber then you will see you changed alot of parts for nothing

 

were you ever able to figure this out? I’m having the same issue. I replaced the qr valve a few weeks back. Went in for brake chamber, had that replaced. …Then the same
Morning as I was replacing brake chambers I heard the leak when brakes applied only thru blur line. Replaced the tpv, still does it. Replaced the treadle valve, and it’s still doing it. I have 2 new brake chamber, new treadle, new qr, and new tpv. Still have figure it out. Unless it’s 1 of the other 2 brake chambers I didn’t replace. I’m lost.

 

I had the air dryer go out and the cross ref one I replaced it with wasn’t purging properly. I was having excessive amounts of water in the tanks. I ended up rebuilding my oem and putting it back on and no water issues since. But because of all that water in the tanks for those few weeks, I was blowing valves all over my truck.