Bobcat 722 hydraulic problem, please help

I recently acquired an old Bobcat 722 skidder. Engine and mechanicals are OK, but hydraulic system has issues. Seems as tho the vane pump is loosing prime. If pump is primed, either by pressurizing the reservoirs, or by pouring fluid into the inlet, everything works OK for a couple minutes, before "charge" pressure falls off. If pump inlet is subsequently opened, at least _some_ suction is present; you can hear it, but apparently it isn't enough to pull fluid up thru the filter.
I have checked for suction leaks, replaced all rubber hoses in the suction circuit, replaced the 25u filter, and filled with fresh fluid. Also disassembeled the vane pump; it _looked_ OK, no scoring, and the vanes fit into the hub was good.
Is it likely that a failing vane pump would cause these symptoms? Anything else I should be looking for? Where does one find parts for something this old? I'll check back here, but please also re. via email. TIA!

ByeBye! S.

Steve Jernigan
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101

On 10/05 you wrote:
>I have a 722 that I keep at my vacation home in Durango.

How does it work for snow removal; that's one of the chores I'd hoped to use it for. Has to be more efficient than teen-aged kids ;-)
Yea, I replaced the 10u filter as well as the 25u one with NAPA parts. Also all of the suction hoses, as well as the lines to the oil cooler. The hydraulic fluid I used was the generic stuff carried by Ace Hardware. Appears to be about the same viscosity as 30W motor oil, but water-clear. I have a service manual that appears to be the original that came with the machine. The manual says either hydraulic fluid or motor oil; turns out that the Ace product was cheaper than even the cheapest motor oil, and came in more convenient 5 gallon buckets.
The poor Bobcat doesn't appear to have ever benefited from maintenance, I think I've spent more time cleaning mung out of the bottom than anything else. Right now, it's pretty well stripped down in anticipation of pulling the hydraulics out to take to a service shop, I've done just about everything I can think of in the way of simple fixes, and anything beyond will require a hydraulic pressure/flow tester. None of the local tool rental places carry one; most don't even know what I'm talking about when I ask. I'm not intimidated (or too stupid to be, anyway) by the prospect of tearing into the pumps, but without some way to verify the functionality of the various components, it would seem likely to be an exercize in futility. The only thing I could hope for would be to find something obviously damaged, but as mentioned, everything seems to work more or less as intended when the vane pump is getting fluid. Sigh.
Guess it would probably be worth the effort to find a high-pressure gauge, and see what sort of pressures the vane pump develops at the point where the main bypass valve opens, but without some way to meter the flow I'm not sure what good the knowledge would do.
What would be helpful would be a used vane pump in known-good condition, or even if I could find a complete used hydraulic pump assembly for a reasonable cost. The local Bobcat dealer tells me a new vane pump assembly is $400-$500! Yikes!!! That for a small handful of steel vanes, a rotor, three machined plates, and a couple O-rings.
Guess I'll do some more searching on the good ol' internet to see if I can come up with anything. Thanx for the reply.

ByeBye! S.

Steve Jernigan
Laboratory Manager
Microelectronics Research
University of Colorado
(719) 262-3101