skidsteer leak down

[tpaulson]

I have a 1993 20hp Lahman skidsteer. It has a problem with hydraulic leak down. The loader boom, bucket rollback, and grapple cylinders all creep downward. It has always leaked down some, but recently it has gotten very bad. You can watch them move downward. If the boom is all the way up, it will be on the ground within 5 min. The cylinders leak down at the same rate with the engine running as shut off.

The only dealer within 300 miles is currently in the process of going out of business, so they said they won't repair it. They thought the cylinders needed seal kits. I find it strange that all 4 cylinders would need kits at the same time. I would think it would be some sort of valve or pump problem. Maybe a check valve?

The skidsteer has 330 hrs. on it. The manual says it has an Eaton 78111 Tandem Hydraulic Piston pump.
http://www.willinet.net/~tpaulson/tractor/skidstr.htm

Does anybody have any suggestion on what the problem may be?
And how major the repair will be?

Thanks

 

[kubmech]

I am not familiar with that brand skid steer, however most implement hyd systems have a common design and generally those circuits are seperate from each other and usually don't share a common leakdown point with each other. Unless you have some sort of loader leveling valve. Does your machine have hyd. self leveling? Or is it a mechanical linkage for self leveling? Do you have a hyd. schematic for that machine?

 

[tpaulson]

I do not have a hyd. schematic. The operator manual has very little info in it. I do have a schematic of the pump itself. I have scanned it in. There appears to be 1 pump with 2 seperate sections. There is seperate fluid reservoirs for the implements and the drive system. There are 3 foot pedal valves for the boom lift, bucket tilt, and grapple fork. How everything is connected to the pump I am not sure.

 

[tpaulson]

2nd page

 

[tpaulson]

3rd page

 

[tpaulson]

4th page

 

[kubmech]

O.K., this could be difficult without a hyd. system schematic but let's give it a shot anyway. It appears that the scan shows the pump for the drive system, which most likely feeds two hyd motors that drive the chains for the left and right wheels respectively. Now at 20 hp it's entirely possible that the charge pump also provides power to your implements as well as the piston pump for the drive, however, with two seperate reservoirs on the machine it leads me to believe you have a seperate pump for the loader and possibly another pump for an aux circuit to the grapple (by the way, is the grapple a seperate attachment that mounts in place of the bucket?) If you have a complete parts breakdown for the machine does it show any other pumps? But all that aside, the main question is do you have self leveling, in other words, when you have a bucket full of dirt and you lift it to full loader height does the bucket atomatically tilt forward to keep from dumping the dirt on your head or do you control that yourself with a combination of lift and dump control?

 

[tpaulson]

It does not have any type of self leveling feature. The grapple is mounted on top of the bucket- see the link from a previous post. I do not have a parts break down list. The manual is very basic(tells how to start the engine, check fluid levels and change filters). It does not mention anything about another pump. I have the part list for the piston pump which I already scanned and a manual for the Kohler engine.

I may have to try to contact the company to see if I can get a service manual, parts list, etc. The company changed owners about a year ago and they are no longer making skidsteers and are not very helpful.

 

[kubmech]

DOH!!!/w3tcompact/icons/blush.gif ckecked the link.

Tim, without self leveling I can't think of a reason for this machine to have a common leakdown point between 3 different functions. You have 3 valves on the floor (just want to get this straight) One controls the loader, one controls the bucket and one controls the grapple. The loader has two cylinders, the bucket has one cylinder and the grapple has one cylinder. Try testing each cylinder for internal leakage by using this method: With all implements on the ground and all hyd pressure bled from the lines by stroking all functions with machine off, remove the hose from the opposite side of the cylinder that powers down. Cap off the hose that was removed. Start the machine and apply pressure to power down the cyl that you disconnected the hose from (place a bucket to catch the fluid) and see if you get a steady stream of fluid from the open side of the cylinder (you will see a stream of fluid initially due to that side of the cylinder emptying out). If fluid continues to flow steadily from the open port, you have verified the cyl piston seal is leaking. If you don't follow me on this procedure let me know and I'll try to explain it better. Now if all cyls test good, we'll have to take a look at the valve layout and see what's going on there, depending on the valve layout you may get drift in all functions from one leaking cylinder. If you want to wait to get a manual to have a look at the schematic. I'll try to help you more then.

 

[tpaulson]

Thanks!
I will give the tests you mention a try and see if I can get a manual. It will probably later next week before I will get a chance to do the testing or call the company with Christmas holiday. I'll keep you posted.