air leak has me stumped...

There is a lot of relays, valves and lines under there. Your gonna have to build pressure up and get under there and hope it happens and find the leak.

 

i bet its the air hose under the cab that runs back to the dryer from the tank. if you look at the dryer and see a hose go from braided rubber to metal inside of the frame. it then goes back to rubber to the tank. leaks when running if it has a hole

 

I had that exact hose break off in February. A bolt was missing from the bracket that held the metal line and the connection to the rubber hose. The vibration caused the hose to separate from its connector.

 

You're going to have to search for the leak. There's literally a mile of air lines and a couple dozen valves in that truck. You're going to have to make the leak appear and then search for it.

Remember, air valves normally sit with the exhaust port open, so if you find a valve leaking air out the exhaust there's a good chance its something else backfeeding it.

 

This^^