Mahindra 4005 Hydraulics

[dnetherland]

I posted this in the Mahindra section but haven't had a lot of input. Any help would be greatly appreciated.

I have a Mahindra 4005 with TAS loader and one set of auxillary outputs. The hydraulics seem to be getting weak over the last several months. Loader lift capacity seems to be less and movement slower. Three point hitch seems slow and will let implements drift down if very heavy. I have changed fluid and cleaned the screen (no filter). Initally function seemed better but after a few hours and when the tractor got hot the problem recurred. I plugged in a pressure gauge to a loader port, then to a remote outlet. When i work the loader or the remote outlets pressure will go up to about 1800 psi and then quickly drift down to 800 psi and stabilize. If I keep working the hydraulics max pressure falls to about 1600 psi and drifts down to 600 psi. Manual says max pressure should be 2400-2600 psi. Fluid is clean and I see no major leaks. The tractor has about 800 hours. Too few to have the pump to fail but when I changed the fluid the first time I noticed a fair amount of metal on the screen. My thoughts are that the rapid leak down must be due to internal failure of the pump or failure of a pressure relief valve. There is a fast, slow control on the hydraulics which I would think acts as a pressure relief valve. I've cleaned it and set it to the fast setting and it has made no difference. I don't think the pressure relief on the loader is the problem since the three point lift and auxillary hydraulics are affected as well. I suspect the pump is bad. A new pump from the dealer is $700-$800. Can these pumps be rebuilt? Is it relatively easy to remove and reinstall a rebuild or replacement? I would appreciate any input before I spend $800 dollars on a new pump.

Thanks
Don

 

[J_J]

Where did you put the gage? If your valve is leaking, or a relief valve is not working properly, I don't think you will be able to read true pump pressure.

Fast/slow operations, is dependent on hyd flow, and it probably switching between reg flow and restricted flow.

 

[Egon]

Fast/slow operations, is dependent on hyd flow, and it probably switching between reg flow and restricted flow.

Hydraulic flow would definitely be affected by a worn out pump.

Just a suggestion but have all screens and filters been checked again.

 

[dnetherland]

JJ

The way I measured the pressure was to disconnect one of the loader lines (the one that extends the cylinder fully). I then moved the joystick to raise the loader and held it in position. The pressure guage would then read about 1800 PSI and quickly leak down to 800 or so. I then plugged the gauge into the auxillary outputs and moved and held the valve engaged. Same results--pressure went to 1800 PSI then quickly drifted down. Anything else I should check. I'm not sure exactly what the pressure relief valve on the loader looks like or how to adjust it.

Thanks
Don

 

[dnetherland]

Just to update, I removed and cleaned the pressure relief valve on the loader control valve. I then plumbed a T fitting inline between the pump and the loader valve. Same results. Pressure would go up to 1800 and rapidly drift down when holding the valve opene. I was able to adjust the pressure relief valve but if I adjusted the pressure over about 1200 then it would rapidly leak down. With the pressure set at 1200 pressure seemed to hold. I'm still not sure if this could be due to a bad pump but I am starting to suspect the pressure relief valve. Any suggestions?

Thanks
Don

 

[J_J]

Since you don't know if the reliefs are good, about the only way to test the pump on the tractor, would be to put a relief valve across the pump, and then add a needle valve to control flow and pressure. If you know the pump pressure, you would set the relief, or install a fixed relief. that has a pressure relief below the pump rated pressure. Put the gage before the needle valve. Open the needle valve all the way, and start the tractor. As you start to close the needle valve, the pressure will increase. If the pump is good, the pressure will build up to the relief pressure. If it does, then you know the pump is good.

That fast/slow thing, is that a separate valve?

 

[DiskDoctr]

Have you tried disconnecting the hoses for the FEL and testing with the 3PH only?

Depending on the setup, it may still depend on the FEL joystick (PB), but it would eliminate all the cylinders on the FEL for troubleshooting.

For the hydraulics experts: Would disconnecting the line coming from the pump from the input on the FEL valvebank and using a union to connect that hose directly to the hose coming out of the FEL valve PB port be okay to use as a test to the 3PH? Would it hurt anything?

If okay, this would bypass the FEL valve bank completely and test with only the pump, 3ph, and possibly any remotes.

Thoughts?

- JC

 

[J_J]

You need a relief valve somewhere. Does your 3pt have one, or was your FEL providing the relief for the hyd sys?