MTVR air leak at vent hoses

[MAdams]

When I press the service brakes, I am getting air hissing out of the vent hoses behind the cab. I'm guessing its a torn diaphragm on one of the brake cans. What is the quickest way to diagnose?

Wes, if your watching, this pic is for you lol

 

[mk2spyder]

I get the same thing on mine, what was the resolution?