Cab will not raise

[Ineedatruck]

The cab lifted fine until today.

1. I get a mist from around the air/hydraulic pump.

2. I am also unable to raise the cab using the hand pump.

I was thinking I needed to rebuild the pump based on other threads. Is the pump being bad why the hand pump is also not working?

Thanks.

 

[MugOfPaul]

Are you sure the mist isn’t coming from the cab lock/latch? The fluid passes through that on the way to the lift cylinder and it’s very close to the same area as the pump.

 

[GeneralDisorder]

What's the fluid level? The AOD pump not working should not affect the hand pump unless the system is low on fluid.

Mist from the vent is considered normal for these. It's mentioned in some of the TM's and in at least one edition of PS Magazine.

That said - they always need rebuilt - there's two seals in particular that are a light yellow colored translucent material that disintegrates into yellow pellets and clogs up everything including the back side of that sintered brass vent.....

 

[Ineedatruck]

What's the fluid level? The AOD pump not working should not affect the hand pump unless the system is low on fluid.

Mist from the vent is considered normal for these. It's mentioned in some of the TM's and in at least one edition of PS Magazine.

That said - they always need rebuilt - there's two seals in particular that are a light yellow colored translucent material that disintegrates into yellow pellets and clogs up everything including the back side of that sintered brass vent.....

I am low on fluid.
I did confirm the mist comes from the pump. I will watch the level closer and find a kit.

Does it matter what hydraulic fluid I use?

Thank you for your help.

 

[Ronmar]

Yea if the pump pumps and nothing moves you either are not making pressure(low fluid/bad pump) or the pressure is not staying in the circuit(fluid leaking out or across from supply to return).

basic rule of hydraulics, the fluid must flow...

 

[Third From Texas]

Get both kits.
The Pump Rebuild Kit and the Latch Rebuild Kit.

The latch misting fluid and causing a pressure loss is just as common (if not more so) than the pump.
May as well renew both because when rubber bits start to go, it's time to watch the others (and the latch kit is cheap).


As far as fluid type, it's been several years and I'd have to look it up in the TM but iirc I just use AW-32

 

[Third From Texas]

Also, note that there are two fluid reservoirs for the system (assuming that it's not a winch truck).
One is by the pump and the other is below the hand pump.

If you have the standard cargo bed, both are easy to access (an M1079, not so much).

But you want to keep both tanks filled when it comes time to bleed air.


Also....and so you don't DIE....

NEVER open ANY part of the hydraulic systems (filler cap, hose, valve, fitting) with the cab only partially raised.
The INSTANT you crack open a hose or fitting, you vent the systems and the 5000lb cab will come down in a flash.

And it can land on your head.
And that's how Chucky got the way he is. ;p

Seriously though, you'll want to do any hydraulic work with the cab either FULLY down or FULLY up.
NEVER anywhere in-between.