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Problem to Cab Air Springs
- Thread starter Lifeson
- Start date
Ronmar
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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…
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…
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.
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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
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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…
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…
Last edited:
Sorry, what is the PPV?
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Pressure Protection Valve. It's a little spring loaded diaphragm valve off the side of the wet tank - between the tank and the dryer. It has what looks like a bolt sticking out of the top of it - that's for adjusting the pressure that it withholds from it's downstream port. Usually about 80 to 85 PSI. This prevents anything downstream of that valve from draining the tanks too low for safe brake operation. Thus "protection" valve.Sorry, what is the PPV?
Ronmar
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Yep, looks like a pressure regulator hamging on the side of the tank. Inboard of that tyere should be a T fitting woth a 1/2” and a 1/4” line on it. The 1/4” is your cab air suspension feed…