Re: Leak in Air Brake - How to test?
Park somewhere quiet, run it till the air tanks are full, shut it off, go under and listen for hissing. A lot of times it's just a matter of tightening fittings somewhere. If you can't hear anything, get a spray bottle, fill it with water and dish soap, and spray every air line and tank fitting you can find. Anything that's leaking will start bubbling up.