953 LPG 20Z new pump cartridge but weak lift cylinders

Machine had been whining, and a new vane pump cartridge fixed the whine.
Fluid was black, so new fluid and filter.
Bucket tilt power seems ok, but lift cylinders too weak to rip up dirt or lift a good size tree more than about half way up.

Thinking it might be a relief valve, and thinking type 1 valve.
Guessing the lift head end relief valve is the one sticking out horizontal to the right closest to the filter - could I reach in through the filter hole and try cranking it down a bit first?
9J-0458?

What's the best way to check pressure?

William

Check the cyls first. Push down and see if they will hold the machine off the ground for long, then hold a load of dirt up, with lever in hold both times.
Later Bob

That's the first thing he did, pick up a tree and let it sit in the air... and pushed the bucket down... he has also fairly recently rebuilt all the cylinders. It's the second engine on the loader but I don't think anything in the hydraulic tank has ever been touched. Interesting, I read last night, that that little tank and valve body weighs 350 lbs... it's a lot thicker steel than I thought LOL...
William in GA

I'm with Bob on this one, I would lean towards a worn or damaged cylinder bore

Pj

On second thought, doesn't that machine have 2 pumps ? It's been a long time since I worked on one of the older machines...... If I remember right the implement pump also controls the swash plates and has something to do with the undrspeed valve etc....

Does the machine travel at normal speed ? How about while operating bucket/boom ?

Pj

These are the relief valves I was wondering about - but not sure the best way to check pressure going to the head end of the lift cylinders.
If the cylinder bores are shot it wouldn't hold a tree up in the air though would it? Or do you think under high enough pressure and out in the middle of the cylinder, there is enough wear for oil to only bypass the piston WHEN it's in that position AND under high load?
How can I check for bypass in the half way up loaded position? Crack the line on the rod end and look for leaks?? (or would return oil back flow from somewhere else and look like a leak...

Relief valve (26) is the line relief for the head end of the lift cylinder.
Relief valve (25) is the line relief for the head end of the tilt cylinder.
Thanks for the input guys
William in GA

Pj it's a 953 earlier model with one vane pump for the hydraulics.
The machine travel is fine, and the bucket tilt power is fine. Stick the bucket in the ground and the tilt cylinder will pop up the dirt, but try and raise the boom and it doesn't have the power to rip up the dirt. It feels like only half pressure is getting to the lift cylinders - why we were suspecting the head end relief valve.
It doesn't look like it can be switched out though, without pulling the tank. I don't know if I can reach down in the tank through the filter hole blind and get everything apart - anyone ever tried this without pulling the tank?
William

Bill you can put a hose and gauge on the pump outlet, should have fitting. Stall all circuits both direction, Lift, lower tilt back and dump at low throttle and compare pressures. Then compare to pressure at full throttle. If it holds the load up then go in through the filter hole and pull the head end line relief valve.
Later Bob

I have seen a bad seal on the relief valve act like you are describing

Resurrecting an old thread here. I have the same problem. Bucket holds fine up in the air, or pushing down. But no lift power intermittently. Thought at first low oil level, checked that it's fine. Tilt circuit works fine. Found this thread doing some research and was hoping someone would know if its reasonably feasible to go through the filter hole to pull the valves and if so if the reliefs are a replacement part themselves or do they need to be rebuilt. If not is there a certain procedure to removing the tank and valve assembly or just start pulling pieces til I get there?

Thanks
John

It's hard to get to the line reliefs and impossible to get to the main relief through the filter hole. Unfortunately this is one of those jobs where you can't randomly swap valves around in the tank and hope you hit on the right one. As per Bob's advice from last year, put a pressure gauge on the test port at the pump outlet and work out if any or all the circuits are down in pressure.

If you decide the problem is in the hydraulic tank, it's much easier to remove the fuel tank and then split the hydraulic tank where it sits.

wmshooke said:

Machine had been whining, and a new vane pump cartridge fixed the whine.
Fluid was black, so new fluid and filter.
Bucket tilt power seems ok, but lift cylinders too weak to rip up dirt or lift a good size tree more than about half way up.

Thinking it might be a relief valve, and thinking type 1 valve.
Guessing the lift head end relief valve is the one sticking out horizontal to the right closest to the filter - could I reach in through the filter hole and try cranking it down a bit first?
9J-0458?

What's the best way to check pressure?

William

Click to expand...

Did you ever figure out the issue with your 953??

jaysksmith , look at my thread on my 943. The set up is the same as a 953. We had the tank off , valves out etc. My pump was putting out just shy of 3000 psi.