Another Lift Cover issue.

[bobsphotos]

I also have an issue with my 861 Lift Arms after rebuilding the lift cover. The original issue was that the lift arms did not lift very far and in position control, the arms just bobbed up and down.
I pulled the lift cover and found that the cam follower pin was worn half way through.
I replaced the pin and changed all ? rings, including 鼎NH rings for the unloading valve, lift piston, and check valve. I also replaced the 徹 rings between the Ram Cylinder and the cover.
I did not make any adjustments to the linkage and put the cover back on. At that point, I found that the control lever had no effect for the first 1/3 rd of it's travel and the rear implement still bounced.
I pulled the cover back off and tried to make sense of the directions on how to adjust the linkage. I just plain gave up and tried to use common sense to make the control lever more responsive.
Fast forward to putting the cover back on:
1. All info is in Position Control.
2. The control lever now responds as it should.
3. The load still bounces about an inch up and down.
4. There is no oil draining from the ram.
5. If I lift the load and stop the tractor, the load drops slightly and then will stay there for 24 hours.
My first thought was a bad check valve, but I think if it was bad, the load would not stay in place for 24 hours. Should I purchase the Zane Sherman adjustment kit?

Any and ALL thoughts will be appreciated.
BobW

 

[Dollar Bill]

Your description is typical for a worn cylinder as the greatest wear occurs at the top. When parked, it leaks down where piston is in a tighter section of the cylinder and holds the lift in position. When running, leak occurs, lift drops and then self corrects and the cycle repeats.

Mount your heaviest implement and do the leak test again. I think you will see a very minor leak from the ram.

If you still have full lift capacity and considering the expense of a new cylinder, most will tolerate the lift bobbing as a minor nuisance.

 

[bobsphotos]

Your description is typical for a worn cylinder as the greatest wear occurs at the top. When parked, it leaks down where piston is in a tighter section of the cylinder and holds the lift in position. When running, leak occurs, lift drops and then self corrects and the cycle repeats.

Mount your heaviest implement and do the leak test again. I think you will see a very minor leak from the ram.

If you still have full lift capacity and considering the expense of a new cylinder, most will tolerate the lift bobbing as a minor nuisance.

I hear what you are saying but the ballast box hooked on the back bounces at any height. 1" off the floor or at full height. When I changed the "O" Ring on the piston, the bore looked to be in fine shape. I did not check it with a bore gauge but it had no scoring at all.

 

[Dollar Bill]

bounces at any height. 1" off the floor or at full height

With this new information, I would suspect the control valve isn't sealing properly. With your ballast on the lift and engine running, remove the hydraulic fill cap under the seat and look for a very small leak.

There are 4 valves in the lift system: Control Valve, Unloader Valve, Check Valve, and Back Pressure Valve. Its the unloader valve that seems to give the most problems. While you have the top off, pull it and replace the O-ring. Double check to ensure you have the correct O-ring and verify the valve moves freely in its bore. Don't use abrasives or wire wheels while cleaning up the valves or bores. Also make sure the control valve moves smoothly. I would leave the check and back pressure valves alone for now.

The green colored path in below photo must hold without leaking. Somewhere along that path yours isn't holding which is causing the lift to cycle. Based on your recent description, I would suspect the control valve.

 

[bobsphotos]

So, in reading this afternoon in the I&T Shop Manual, I made a discovery.
This is what the manual says regarding the retaining plate of the lift cylinder.
When reinstalling retainer plate(48), use new gasket (47), and BE SURE that sealing washer (49), is installed under cap screw located between control valve spool and cylinder bore. RENEW WASHER (49), if damaged in any way.

I have no idea what this sealing washer is about but I doubt I put it back on. I know I did not replace the gasket. The special sealing washer is no longer available so I will have to get something from a place like McMaster. Anyone have any ideas about this washer?
Thanks ALL.

 

[Peter 315]

So, in reading this afternoon in the I&T Shop Manual, I made a discovery.
This is what the manual says regarding the retaining plate of the lift cylinder.
When reinstalling retainer plate(48), use new gasket (47), and BE SURE that sealing washer (49), is installed under cap screw located between control valve spool and cylinder bore. RENEW WASHER (49), if damaged in any way.

I have no idea what this sealing washer is about but I doubt I put it back on. I know I did not replace the gasket. The special sealing washer is no longer available so I will have to get something from a place like McMaster. Anyone have any ideas about this washer?
Thanks ALL.View attachment 544615

Maybe a copper washer will work

 

[bobsphotos]

Maybe a copper washer will work

That would be my guess. I just hope someone can chime in and talk about the importance of this soft washer and a perfect gasket.
Bob W

 

[Peter 315]

You can buy some gasket paper at the auto parts store and some copper brake caliper washers

 

[bobsphotos]

You can buy some gasket paper at the auto parts store and some copper brake caliper washers

I have gasket material and can purchase a sealing washer but I am in hopes that someone will chime in with some info re: this gasket and sealing washer. I am confused as to why only 1 out 3 cap screws have to be sealed.
Bob W

 

[Peter 315]

I have gasket material and can purchase a sealing washer but I am in hopes that someone will chime in with some info re: this gasket and sealing washer. I am confused as to why only 1 out 3 cap screws have to be sealed.
Bob W

I think all 3 but it only shows one in the photo