Problem to Cab Air Springs

[Lifeson]

I'm having a problem with the cabin air springs because when the leveler is active and I release the handbrake, the springs sag. Does anyone have any idea why?

 

[Ronmar]

Sounds as if something is not plumbed correctly.

the hydraulic/air control manifold that controls the air operated hydraulic pump and the cab air suspension should have 2 separate air sources. The air/hydraulic pump control source comes from a remote control valve that disables that source when you release the park brakes(keeps a failure or someone deliberately raising the cab while driving the truck) the cab suspension should be supplied directly from the wet tank.

the manifold should have four, 1/4” lines attached. One in from the wet tank and one out to cab suspension height control valve. A 3rd line comes in from the remote control valve(controlled by park air) and the 4th line out to the air op hydraulic pump… It sounds as if your 2 input sources are connected to the wrong ports on the hydraulic/air manifold…

 

[Lifeson]

Hi Ronmar, you're always the one who gets me out of trouble! The problem is that I removed the air/oil pump like Chad did; I think you know who that is. It worked normally at first, but now it's been having this problem for a while. I tried removing the leveler, thinking that was the cause, but it wasn't. I'll try to get you to connect it, hoping I can find a solution.

 

[GeneralDisorder]

Just run a line from the PPV straight to the leveling valve. It just needs to only get air when the wet tank is safely above the pressure protection valve and the leveling valve does the rest for you.

 

[Ronmar]

Well the cab deflating when park brakes are released tells me the cab is connected to the wrong source.

i basically did what General suggested when i deleted my AOP hydraulics. On the rear side of the wet tank there should be a device that looks like a pressure regulator. That is the pressure protection valve(stops flowing air when tank drops to 85PSI to save air to feed the brakes).

On the inboard side of that device you should have 1 large and 1 small(1/4”) lines Td off. The large line goes to the cab to feed CTIS and fan control, the 1/4” line is your cab suspension supply. Connect that line direct to the height control valve on the cab suspension. I got fancy and added a valve to allow me to turn it off in case i develop a leak…