NAA hydraulic no pressure

[Ed Ridgeway CO]

I connected a hose from my pump and ran it back into the lift to see if the pump was pumping.
This is how much oil is being pumped at idle.
I put a pressure gauge in place of the hose and ran the engine.The lift will not come up no pressure on the gauge and no oil leaking anywhere inside or out.I just don't understand.Ed

 

[souNdguy]

It would be normal to see no pressure on the gauge, as oil is dumping to sump under the lift cover.

normally to pressure test the system, you CHAIN the lift arms to the axle, then run the lift up.. the gauge will then show relief pressure if everything is ok.

since your arms don't move, my guess is that the unloading valve is stuck.. that's a common issue.

very much less likely is that the pump is shot and making volume, but can't support any pressurized load.

I'm betting on the sticky unloading valve just dumpoing all yer oil to sump as if you weren't dinking with the 3pt control.

soundguy

 

[Ed Ridgeway CO]

There is no oil being dumped back into the sump.
I can reach my hand in and with a small punch Inserted into the hole in the end plate I can feel the unloading valve move back and forth when I move the position lever up and down.When I move the lever down the unloading valve moves toward the front and oil flows out the back pressure tube.When I move the lever up the unloading valve moves toward the back and no oil flows from the back pressure tube.But the piston doesn't move and there is no oil dripping flowing squirting anywhere inside the housing.
I also put a rebuild kit in the pump.
Could it be I have the wrong hydraulic fluid?

 

[JMOR]

Ed, I have been following your situation for more than a month & I do feel for you. From my perspective, it seems like the pump, despite all that you have done with it. Some will have suspicions that the fluid is dumping back into the sump, somehow, but I know that you have really tried to verify that it isn't. If I may, might I suggest that you extend your earlier bench test one step further, as it might reveal something. You applied air pressure to the inlet to the lift cover & things operated on the bench. Now, apply air pressure to the test port down on the right side of hydraulic housing and see if lift still works as it did on bench. At this time, observe whether or not fluid is being forced backwards thru your pump from the outlet, back thru suction to sump....good pump outlet valves should not allow that to happen. Also, with air you may see bubbles, where a leaking fluid alone might be missed. Or you may hear an air leak. Just a few thoughts that might be helpful before you slip past the last knot at the end of your rope.

 

[souNdguy]

No.. hyd fluid wouldn't be causing these problems. could have 10w atf fluid int here and have it work.

Are you sure no oil is making it downt he front o fthe sump wall.

last time I had this discussion with a guy with an NAA with this EXACT SAME proplem, he swore up and down 25 times no oil back tot he sump. after many disassemblies, he found oil wass shooting out the opposite end fromthe piston and ruinning downt he front of the sump.. volume was low enough that he thought it was just the oil on the sump wall.

if the pump is pumping.. then the next thing to look at is the relief valve.

it;s either relief or te pump if the unload valve IS working and there is no oil tot he lift cover.

soundguy

 

[Ed Ridgeway]

I think I will try that applying air to the test port on the side of the housing.Just for kicks.One more thing,If the tractor sits for a few days When I first start it I can get the lift to go up and down with the engine at a fast idle but it will not go up if I stand on the drawbar.After I cycle it up and down 4 or 5 times it will quit and not go back up.

 

[Ed Ridgeway CO]

I wish I could see oil squirting or running some where but I have a light bulb in the dipstick side and I stick my head in as far as I can get and with a mirror in the pto shift side I cannot see any oil but a small drip coming from the hole in the end plate where the unloader valve is.
I have the oil level down to where I can see the relief valve and no oil is coming out of it.I can reach my hand down into the oil and put my finger over the end of the back pressure tube and feel oil coming out when I lower the position lever and no oil coming out when I raise it.
Whenever the lift does come up and I lower it I can see the oil running down the front wall of the housing.

 

[JMOR]

"One more thing,If the tractor sits for a few days When I first start it I can get the lift to go up and down with the engine at a fast idle but it will not go up if I stand on the drawbar.After I cycle it up and down 4 or 5 times it will quit and not go back up."

Not of much significance to my thinking. If it won't lift a man, then it isn't doing much.......maybe it is just cold enough (thicker fluid) to make it do a little something?

 

[souNdguy]

ok.. so not relief.. and not leaking out.. and when down, unloader is dumping it like normal.

next test.. that oil coming out when lift lowered.. can you stop it with your finger? if so pump is making volume with no real pressure.

soundguy

 

[Ed Ridgeway CO]

I'm starting to think that maybe it is the pump also,though I don't know why since I did put a rebuild kit in it.When I rebuilt the pump I did find broken springs and other junk in there.Did I also mention that I found a plastic plug like you find in new pumps that was left in the pressure out let with only a small hole in it.I know that wasn't the cause of the problem but just 1 of the many little things I found.
So any ideas on how to fix the pump?

 

[souNdguy]

IF it is the pump, and it's making volume, but has no capability of pressure.. then I'd take it apart and make sure the valves are sealing.. as it sounds like it would be bypassing if it's not pumping.
by the way.. I'm NO pump rebuild expert. i understand how they work.. but as far as troubleshooting one.. aside from the obvious stuff like no broken parts or ill fitting parts.. and the obvious like bypassing a seal.. etc.. I'm not gonna be much help for ya.

one last thing.. make sure the drive is good. I've seen a pump with a bad drive shaft that actually pumped as the shaft spun with no load.. but under load, the pump didn't actually turn.

could likely try that with your hose trick..

chain 3pt arms down, run lift lever up.. that will block oil on that end, then have your oil line aiming into the sump, with a pressure valve t'd in.. then crimp that line and see if it will make enough pressure to blow the line off the nipple.. or just start bypassing right there.

please post back with details... this is an interesting delima..



soundguy

 

[JMOR]

It was mentioned that the pump shaft not turning under load as a possibility, perhaps key sheared, and & thought I might suggest the possibility of observing for pump shaft rotation here: