How to tell when airbags need to be replaced?

Unhook leveling valve and manually overinflated the bags beyond normal
Hopefully you can see base of the bags as they uncurl from bottom seat

 

I wonder if those bags are the correct ones. Maybe they are to short for application. May want to cross reference part # with originals.

 

Set the lift axle down and see if it still looses pressure. That amount in a couple hours isn't bad. Annoying sure.

There is no leveling valve on the pusher axle, just a pressure regulator. To check you main bags un hook the leveling valve and raise the bags up. That will also over extend you pusher bags so you can check them all

 

I’ve had air bags leak, always at the base. Accidentally found one in the rain, it was whistling. They may even stop leaking when more air is added, since the leaks on top of the base. Way over inflating them can cause a leak at the base. Hard to find. Have to spray bottom of bag, at base, maybe at different heights. Yours look fairly new. If they’re not leaking, or dry rotted, they’re good.

 

Red circle is the lift axle air bags.



Spray these with soapy water.