I’ve got a 45’ Eagle towable manlift and bottom boom is leaking down.

[oldnslo]

I think the solenoid valve is used to select whether the upper or lower valve stack gets flow from the pump.

 

[BeezFun]

beezfun,
Ok I’ll try what you suggested however if I raise both cylinders and then turn the engine off won’t both cylinders go down when I manipulate the valves to relieve pressure?

No, manipulating the valves will relieve the high pressure on the hose before you remove it so the fitting doesn't fly off and spray you with oil. Removing the hoses will completely separate what's going on, if the cylinders leak down you know the check valve is not working properly.

I’ll look into the valve y’all are talking about on the cylinder itself. Will there be a holding valve on both the upper and lower or just the lower?

Yes, there needs to be a holding valve on both cylinders. The location that the hoses attach to on the cylinders will almost certainly be the holding valve. The logic is you don't want any hose failure to allow the cylinder to move, so the holding valve is hard plumbed directly to the cylinder and the hoses connect to the holding valve.

 

[Puppypunter]

Thanks guys for all your help, I will try what beezfun said tomorrow and report back.

 

[Puppypunter]

Ok I tried it and your right, on the uppercylinder one I shut the engine off and manipulated the valves it did not move.obviously the lower cylinder was moving already anyway but it didn’t move any faster when I moved the valves. So I then disconnected them at the controls and by this time the lower was already cradled. Here’s what it looks like. One from the front and one from the back. It looks the exact same on both sides. Could it be just an oring? Why does it most certainly look like it’s adjustable?

 

[leonz]

Do you have a hydraulic repair shop nearby?

You could have a number of problems but
most likely the worn spool valve banks need to
be replaced as they typically are the things
that fail because the square cut o-rings wear
down over time and the spools surfaces also
wear over time and the entire spool valve
bank needs to be thrown in the steel bin
to be recycled.

DONT BUY a "rebuilt spool bank" because the
replacement spools will leak much sooner
than they should as the old valve body for
each spool was enlarged slightly to mate
with the new spools and square cut o-rings.

Your man lift may have pilot operated
check valves attached to the cylinders
to prevent the collapse of the upper and
lower booms in the case of a hose failure.

If you have a pilot operated check valve that
has a leaking seal /check ball that may very
well be the cause of your current trouble.

 

[BeezFun]

Ok I tried it and your right, on the uppercylinder one I shut the engine off and manipulated the valves it did not move.obviously the lower cylinder was moving already anyway but it didn’t move any faster when I moved the valves. So I then disconnected them at the controls and by this time the lower was already cradled. Here’s what it looks like. One from the front and one from the back. It looks the exact same on both sides. Could it be just an oring? Why does it most certainly look like it’s adjustable?

The photos you took show the pilot operated check valve, you're looking at the end of it. It's not user adjustable, that's to set the operation of the pilot valve so it opens at the right pressure. Can you clarify which problems you're wanting/needing to solve? Is the main problem that the lift drifts down while you're up in the basket? Or is the main problem the oil leaking and slow operation of the valve when you're trying to raise the basket? Those are two completely separate problems. To solve the drifting down problem I believe you will need to replace the pilot operated check valve(s). I just had to replace one on my lift and it was about $100 to give you a ball park figure.

If you're trying to solve the leaking valve and slow operation, that's a different problem. The orings only seal against low pressure, the high pressure seal is provided by the metal on metal contact of the spool inside the valve body. So it's likely that you could replace the orings and it would still leak. Does it leak a lot and do you care?

Regarding the slow operation when raising the lift, that could be several things. One thing that just dawned on me, I think you have single acting cylinders on that machine because of the way it's designed. Are there 2 or 4 hoses going to each cyiinder? If it's single acting there will be a small weep hole somewhere to let out the condensation and any leaking fluid. Are you sure it's not leaking in some out of the way place you haven't noticed? I assume you've checked the fluid level. Has the filter been changed in recent history? It's possible it's old and restricting suction by the pump. If you don't see oil leaking out of the cylinders and the filter/fluid are ok, you need to do some more diagnostics.

 

[oldnslo]

Since the valves in those pictures have have adjusting screws I would lean towards one of them being a counterbalance and the other possibly another pressure control or flow control. It looks like that square base is welded to the cylinder so I would blow all the crud you can out of the counter bores around those valves and carefully remove them. There could be some identifying numbers on them so that can order replacement valves. If my guess is correct you need a 7/8 socket to remove them.

On why functions move faster one valve vs other valve stack is another whole different topic. Is it just the one function moves slower or do all the functions move slower?

 

[Puppypunter]

Yes I guess I should clarify, I’m just looking to get it to stop leaking down, the reason I mentioned the upper controls being slow is I thought I had a spool problem and if that were the case how would I go about getting it to flow alittle faster in the event I had to buy new spools. (Now that I think about it there is some kind of adjustable control valve at the upper spools, that look similar to these “pilot” valves. but enough about that)

I took both sides out and they are identical, I got out a mic and checked to be sure and as far as I can tell they r identical.I couldn’t see any numbers on them but I’m sure there r somewhere.

There r two hoses going to each cylinder, with a third threaded hole blocked off, is this to bleed the cylinders?

On the fluid snd history of the machine when I got it rain had got in the tank via a leak in the flange on top the tank. My buddy works on an oil rig and brought me 55 gallons of 68 something or another and 5 gallons of hydraulic oil additive (I’m guessing it’s zinc and or other friction modifiers?) he also brought me like 10 filters that I had to replumb so they would fit. (The original filters were much smaller)

I set out trying to get all the moisture out of the system, so I drained the tank, drained as much as I could out of the cylinders by pulling the hoses off and then filled it back up with a new filter, I did this several times over this past summer and I think it’s all out now, (20 gallons and 4 filters later) so I don’t think theres anything wrong with the fluid or filters.

when I pulled out what I’m calling the “red” side looking at the nose of the valve there was a sliver of steel that was caught under the seat, im guessing this would cause it? Or could cause it? Problem is the valve is so stiff I don’t know how to make sure I got all of it out and it didn’t just break off at the seat. Please advise. I really appreciate all of you helping me out with this.I would rather not spend a few hundred dollars if I don’t have to.

 

[Puppypunter]

Here they r

 

[Puppypunter]

There are only two hoses going to each cylinder.