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

If it does it right after you get out of the cab then stops that's normal. Its just exhausting a bit of air to bring the height back down to spec since your bodyweight is no longer in the cab.

 

Probably is the valve. They get old and tend to stick just a bit. Usually inconsistent. After it sits a few minutes and levels out, try to wiggle the arm on the valve, back and forth, up and down. If it’s a bit loose, you can usually make it leak or make it stop leaking by wiggling the arm. Also check the bushings on the rod, Make sure none are missing, or worn and loose. along with the bracket it bolts to. Another common culprit for inconsistent leaking is an air bag. They’ll leak around the bottom. Can be very hard to find. Soapy water, a good ear in a quiet place, and running your hand around suspected leaks, feeling and listening for air leaks. It can be leaking from anywhere, just need to find it.

 

Good. I had one leaking on my trailer recently, along with the parking brake valve on the tank. Spray some soapy water on that valve, if you have to, wiggle it around. Probably what’s leaking.

 

Same here, I had one leaking from the bottom