2005 Western Sterling spring brakes won't release

check park brake/trailer supply tank pressure.

Unhook red glad hand and press red knob. if no air goes out from red glad hand - check park brake tank valve. it may stuck.

Other problem - park brake release relay valve - may go bad too!

 

if it is rigid truck w-o trailer - tank #3 (park brake and trailer supply) is used anyway, but smaller.

It may be combined with other tanks with valve inside inner wall, like on freightliner, so inspect air lines to find what is the park brake tank and check for pressure inside with moisture drain valve

 

abs relay modulator is the different thing, check park brake relay. lines from park brake relay run to spring port, not for service brake ports

http://www.suspensionspecialists.com/techinfo/Bendix_Brake_Handbook_2009.pdf



Park tank lines are of red color, park control - yellow

 

Wait a minute...what is a Western Sterling? LOL.

 

Do the brake lights stay on ? The foot valve pedal may be sticking. Pull the cap off the brake camber cageing spring brake hole look at the plate an have some one push the park brake valve in . The plate should move to the back cover. If it moves the problem is on the service side bad valve , foot valve .

 

to check tank pressure I use moisture draining valves. Just pull it!

what is the specification of vehicle? is it class 6-7 rigid truck? I saw Sterling trucks with Mercedes Powertrain (OM906LA engine and 6 st tranny). really it was like conventional design version of MB Atego.

Air system is very simlpe. One supply tank (also used for air syspention) and four air tanks: Primary, Secondary, Park and Accesory tank (sleeper suspention, transmission spliter, seat air suspention).

So things are very simple.