Cab leveling valve dumps air when I turn of my truck.

What model truck? Does this happen immediately after turn the key?

 

What's your air pressure at after its sat overnight? If the tanks are empty or very low then its leaking out somewhere on the truck.

 

You've got an air leak somewhere on the truck. All trucks I've seen have a pressure protection valve and once reservoir pressure drops below somewhere around 75 PSI or so, it no longer allows air to flow to accessories like suspension, cab, seat etc.

 

Take a spray bottle of soapy water and get under your truck. Unless you can already confirm the leak is at the cab bags or leveling valve. Even if your air is leaking someplace else your cab will be dumped when your tanks are empty.

 

I'm thinking he might find 2 leaks. If it was just from the cab suspension then the air reservoirs would maintain pressure once the pressure protection valve closed off.

 

If you hear a small bit of air when you get out and then it stops that’s just the cab leveling itself because you removed your weight from the cab.