Hydraulic lift arms won't lift heavy weight.

Your diagnosis is probably correct - likely a tired pump. Piston rings/cylinders, and/or valves. Quick check - more lift at higher RPM?

Pressure check (5000 lb gauge and high pressure hoses) will verify whether it's pump or lift cyl. (We haven't had much problem with the lift cyls.)

3/8" hex head pipe plug on the left side of the cover under the seat is a pressure port. With 3 point control set to Constant pumping with no flow (3-point arms fully up, remote cyl held fully retracted or extended, or disconnected and control valve moved to operating position), the relief valve should blow (thumping sound), and 2500 - 2700 lb pressure indicated.

Not a difficult fix - you do need a shop manual though, and a day or so to do it.

Parts are somewhat cheaper in Canada, with our 63 cent dollar!

Do you also know those figures by heart for a MF25. I've got a similar problem, replaced all the seals and pistonring but no result.

Willem

No I am not familiar with the 25. But if it's rebuilt, and oil level is above the pump, it should work.

Possibility - is the control linkage working properly? On the 35's and 65's, that is visible through the cover with the oil level stick on it.

And the message below suggests relief valve open. This will be visible by oil blowing out of it.

Later ones have response control on that cover, and I think you should have a manual before removing it - to be sure you get things back together ok.

If your cover has no attachments, you should be ok. If the oil level is full, raise the right rear wheel 6", or drain out a couple of gallons to avoid a mess.

Hope this helps.

Could be that GM is smarter than our suppliers, or quicker to reprice inventories.