I have a old Prentice loader with a bar saw. Last Friday when I used it it worked fine. Today when I started it up and engaged the clutch I have no hydraulics. It has a tandem pump with two circuits, one controlling each joystick. Neither circuit seem to have oil moving. Once in the past I had a hose peel apart inside and stick one relief valve open but this time it is on both joysticks. It was bloody hot Friday and the hydraulic oil tempuature was at 230 degrees when I shut it down. I can see that the shaft coming out of the pump is turning. When I disengage the 353 Detroit clutch I can freely spin the pump with little effort. Does it sound logical that the pump shaft broke just inside the housing when I shut it down or at startup. I always idle it down for a bit before I disengage the clutch on shutdown and on startup I always engage the pump with the engine idling. I heard nothing either time. Looking for opinions on what else it might be before I drain and remove the pump. Its going to be a bugger to get at where it is setting on the landing and I can not move it with the outriggers down. The engine does not appear to pick up any load when I engage the ctutch. Thanks
I do not like being able to spin the pump freely. That is not right.
Gear or vane pumps? Old open center setup, if there's no load the oil just flows through the valves to tank so it's not unusual to be able to turn the pumps by hand, it's just seal drag basically. Does your bar saw have a separate valve, or is it part of the joystick controls? I assume the joysticks are manual linkage to some stack valves? Look for ball valves or shutoff valves that need to be open or closed, these are natural eye catchers for kids and delinquents that think it's fun or funny to screw with a man's livelihood. If there are tank shutoffs that could be it, or some kind of bypass valve? I doubt the pump shaft snapped, but something could have come apart, if it's a tandem gear the drive gears are usually keyed to the shaft, it's remotely possible the heat caused the gears to seize but that's a real reach I think. If you can get a look inside the hydraulic tank see if there's something clogging up the suctions. If the pumps can't get oil they should be growling loud, but next to a screaming jimmy, even at idle, I doubt you'll hear it. Maybe pull one hose from the pump off at the valve, stick it in a 5 gallon bucket, or back to the tank if it will reach, tickle the clutch at idle and see if she shoots good?
It is a tandem gear pump. The hydraulic tank sets right over the pump about a foot above it. It has separate 1-1/4 inch suction lines to each side of the pump. The two 1" pressure lines go one to each of the joysticks controls first. They are the full size power beyond controls, the cab is always over 100 degrees in the summer even with all the windows out From the two controls both pressure hoses go to a diverter valve that runs the saw and then returns to a collector pipe that all the returns connect to, then thru a return filter and back to the tank. The pump makes no noise or vibration. It does have a keyway in the coupler but I can see the shaft is turning on the pump side of the key. Your idea of pulling a pressure hose and trying it in a bucket is a good one. I will try that in the morning. That should tell the story. What's odd is that when I put the boom in the cradle last time I used it all was working fine. Seems odd to break at rest after lifting 2 to 3, 50 ft 16" diameter trees at a time all afternoon. No unusual noise although with the 3-53 who knows if it would be heard.