trailer brakes wont set

Hi bobby, could be moisture in the system, try draining the air tank on the trailer, otherwise, there's a distribution valve above the trailer axles, unit with 4 air lines, one going to each wheel, could be stuck. If anti-lock is involved, I can't help ya.

 

HE says this happens with all trailers. It would seem to be a tractor specific problem. I'd start with the red valve, that's where air comes in and air goes out. There should be a vent where the air exhausts, all the plumbing is on your firewall. Good luck.

 

Oh yeah, duh, I see that now.You are right, something is preventing the air to be released. My 359 had a valve under the cab that the emergency line came from, maybe that's bad. I never had a red button valve go bad, but it's possible. Plugged line? Once, I helped a guy with brake problems, we took the line off a brake chamber, he pushed on the brake, and all this oily water jiz came shooting out.

 

Sounds like you have a QR valve not working, or a probem in the dash valve itself. I had one doing this once and found that the QR valve on the back of the cab (Sterling) was replaced with a check valve. The QR valves were known to leak on those and someone must have thought it was a check valve. It was not letting the air out of the trailer.