trailer brakes not releasing

Does the trailer do this with other tractors? (is this the only trailer you can test with?) What kind of weather are you driving in?

First off, drain you trailer and tractor air tanks. Especially in cold weather moisture can build up and freeze. Also, at night, don;t apply your trailer brakes unless you are parking on a hill. my companies policy is don't apply them unless the shipper requires it.

When we do apply, I'd say 10% of the time they get stuck. Normaly a quick tuck will fix um and get um rolling. For us, the trailer air tanks are rusted and cant be drained. that causes our problems.

 

Is the trailer equipped with a quick release valve?

 

I would be looking at the push pull valve module (red/yellow). They have kits to renew the valve from the front without completely removing the module from the dash.

 

Yes, replace the parking section (piggyback) on that chamber and the service diaphram (pancake) too. Make sure the s-cam rotates freely on that wheel too, bushings could be dry and shaft rusted.

When you release the trailer brakes the line going into the top of QR valve should have air. When you set the trailer brakes air pressure to that line should cut off and the valve should dump. If you find that the control line going to the top of the valve isn't consistently supplying and cutting off air when pushing/pulling the knob, the problem is before the QR valve, possibly the push/pull valve module in the dash.

 

first of all start with red glad hand pressure. Check it with gauge. Must be over 100 PSI with red button depressed.

Other quation - trailer brake confuguration. What year is the trailer? All trailers after 2000 are with PREV (park release emegrgency valve). This valve is designed to keep brakes applied if valve fails. This valve controll service brake chambers (via port 4 on ABS unit) and spring brakes that actuates if pressure in trailer brake tank is lower 90 PSI. Really there are two air systems in trailer - brake system (usually two tanks) and air suspention tank. If trailer brake tank leaks air you fill it with red button depressed, and trailer brake are applied till trailer pressure not over 90 PSI.

so... I sugest trailer air leak ore bad PREV.

Example of new design PREV by Wabco http://inform.wabco-auto.com/intl/pdf/815/01/78/01/971002t2.pdf

really they look different. not all are equiped by manua valves

 

Single cans or double? The next thing is to use the adjuster to spin the S cam once you have filled it with grease, to get the new grease around the bushings.