New Holland T4.75 power star hydraulic problem

[NCJim919]

The loader jerks really Bad when the oil is hot . I have replaced the pump, loader control valve, relief valve, change filter and oil ,replaced all suction hoses on suction side of pump ,changed the quick couplings and switched the hoses on the lift and replaced the cylinder packing . Installed a flow meter on the lift hose, I have 5.5 gallon a minute at idle and it will drop to around 3.5 when it jerks and go back to 5,5 till it jerks again and pressure stays around 500 when lifting . Pump puts about 11 gallon at 1500 rpm’s .Also removed filter housing and piping to check for cracks When the oil is cold it does not jerk the warmer it gets the worst the jerking. I have talked to the dealers around here they were no help. Any recommendations you have will be very helpful.

 

[oldnslo]

Where are you measuring the flow when drops from 5.5 to 3.5 GPM? In pressure line between pump and valve or somewhere else in the system?

 

[NCJim919]

on The quick coupling on the lift cylinder

 

[oldnslo]

Can you move the flow meter to the valve inlet and repeat the test? If flow still drops need to move flow meter even farther upstream until flow no longer drops. That will help point towards the component that is leaking flow. Per specs I see online this has fixed displacement pump so flow is going somewhere, just need to figure out where.

 

[5030]

I have to ask, what kind and brand of oil you are using in the gearbox sump? The gearbox and the pump share the same oil? Hopefully, it's not the low buck TSC crap or is it?

 

[NCJim919]

Can you move the flow meter to the valve inlet and repeat the test? If flow still drops need to move flow meter even farther upstream until flow no longer drops. That will help point towards the component that is leaking flow. Per specs I see online this has fixed displacement pump so flow is going somewhere, just need to figure out where.

the pump also feeds the remote valves that are open center I think

 

[NCJim919]

I have to ask, what kind and brand of oil you are using in the gearbox sump? The gearbox and the pump share the same oil? Hopefully, it's not the low buck TSC crap or is it?

No it is new holland oil

 

[NCJim919]

the pump also feeds the remote valves that are open center I think

I don’t notice it as much when I am lifting a bail of hay. With no load on it at higher rpm it still jerks and the hotter it gets the more it will jerk

 

[LouNY]

Is it only on the loader lift?
What about the loader curl or when using the rear remotes?
If it is only the loader lift and it gets better with more load,
I'd lean towards a seal sticking in the cylinder bore from heat swell.

 

[NCJim919]

Is it only on the loader lift?
What about the loader curl or when using the rear remotes?
If it is only the loader lift and it gets better with more load,
I'd lean towards a seal sticking in the cylinder bore from heat swell.

I replaced the seals on the pistons but not the gland seal and it still jerked I can replace the gland seal I have them in the kits. Do you think the gland seals will make it jerk so bad . The curl works fine

 

[5030]

What weight is it? Sounds like it's too thin when hot. Most smaller tractors are power beyond, not open or closed center. Easy way to tell is to see if a return to sump hose is present. There will be with an open of closed center system. With power beyond, there will be no return to sump (gearbox-transmission hose).

Both of mine are open center so the fluid dump is direct to sump via a return hose.

 

[NCJim919]

I replaced the seals on the pistons but not the gland seal and it still jerked I can replace the gland seal I have them in the kits. Do you think the gland seals will make it jerk so bad . The curl works fine

The remotes work ok o problem

 

[NCJim919]

What weight is it? Sounds like it's too thin when hot. Most smaller tractors are power beyond, not open or closed center. Easy way to tell is to see if a return to sump hose is present. There will be with an open of closed center system. With power beyond, there will be no return to sump (gearbox-transmission hose).

Both of mine are open center so the fluid dump is direct to sump via a return hose.

There is a return on top of the 3 point hitch housing no power beyond . The oil is new holland for transmission and hydraulic systems

 

[5030]

Sounds like Lou is on the right track...

 

[NCJim919]

i will replace the gland seal and send update

 

[K5lwq]

I replaced the seals on the pistons but not the gland seal and it still jerked I can replace the gland seal I have them in the kits. Do you think the gland seals will make it jerk so bad . The curl works fine

I would swap the hoses between the curl spool and lift spool so that moving joystick left or right raises the loader. If problem goes away on lift but moves to jerky curl then the directional control valve is the likely culprit.

 

[NCJim919]

I will try that also I will have to install the suction pipe and filter base they are off the tractor now Thanks

 

[NCJim919]

I have removed the suction piping and checked the flanges for cracks and also removed the filter base housing did not see any signs of a crack. Remove both lift cylinder and replaced gland packing. And it still does the same thing

 

[K5lwq]

I have removed the suction piping and checked the flanges for cracks and also removed the filter base housing did not see any signs of a crack. Remove both lift cylinder and replaced gland packing. And it still does the same thing

Did you try Swapping the hoses to eliminate the valve?

 

[NCJim919]

No but I did replace the mid mount valve with a new one from new holland