Slow seting emergency brakes

It is an ABS trailer?

It sounds like the Parking Brake Quick Release Valve. (page 21)

Look at this Bendix pdf. It has good info on all the valves and what each does, pictures of each valve, diagrams, and troubleshooting. If they ain't dirty the spring in the valve can break.

http://www.wsafc.org/WSFMA/Shared Documents1/Bendix Air Brake Handbook.pdf

Pages 21, 25, 26, 28, 31, 32, 58-60

 

check trailer PREV valve. It may be located on front trailer wall (generally on EU Tint ore on drybox) ore on frame. I do not really know the brand of valve (Bendix, Haldex, Wabco, Knorr ore other), but read here how does it work http://inform.wabco-auto.com/intl/pdf/815/01/78/01/971002t2.pdf

When you pull out red button and no supply air PREV valve apply air brakes on trailer and if trailer loose air lower 80 PSI spring brakes are applied.

The other problem may be hidden in park valve in cabin. It supplys TCM (trailer control modul) with air when red button is pressed

 

Some people ( us) run hoses on the trailer to release through the tractor, and that takes a good 30 seconds for the brakes to apply Unless you pull the tractor only then trailer

 

It is not legal. In case of accident related with brake failure driver will be convicted.....

 

We have to trailers like that but they're old and that was the only solution anyway

 

Really there are current ECE and DOT regulations about trailer safety and brake systems. For example now on tridem trailers to axles must be equiped with spring brakes, before - only one was enought and I remember trailers w/o spring brakes. PREV, ABS/EBS must be installed on any trailer. It is legal thing. PREV is not just park brake valve, it is more sufisticated thing to apply brakes when glad hand separates on run.

 

Yep, page 31, trailer spring brake. SR-5 is the simple example, becouse now many trailer makers install trailer spring valves with manual valves to let disable/enable trailer park brakes manually (trailer air system is full, but no trucktor).