Losing air break pressure while ilding

Simple answer.

You have a air leak.

Now the fun part is trying to chase it down.

Spray all fitting and air lines with Windex or soapy water and look for bubbles.

See bubbles, fix leak.

 

Listen for when it cycles off again or finishes building pressure and if u here a loud pop or hiss check the slack adjusters for play. I think I remember having a similar problem in same setup before. Could be bent or corroded bleed valve. Best bet is to let it build up pressure. Turn off truck and crawl under it and do like post above said to do.

 

Air it up to 130 lbs, throw it in gear and shut the truck off with the brakes released and the tires chocked. Probably a brake chamber leaking or a bad purge valve on the dryer.

 

What year and model is this truck? Ant spec'd add ons? 6 wheeler?

 

Build up your pressure and turn the truck off. Turn the key to auxiliary and press the brakes once and leave it held down. While u do this keep ur eyes on the air gauge and determine how fast it depletes can sometimes give u and idea if it's a major or small slow leak.