I have almost been through the entire hydraulic system on my 287B. I have replaced the controller and capped off the other valves such as the lift level diverter and the manual lowering valve still drifts in both lift and tilt. I have no leaks in the system it must be bypassing somewhere and I have rebuilt all cylinders lift and tilt. I could use any help from anybody that has had this issue with there cat. The next step from CAT was to check the main valve I am going to tear into that tomorrow. Thank you TJ
What is drifting? 2" in an hour? or the whole travel length in a couple hours? Can you post the parts list for the valve? I would be looking at the relief or the holding poppets if it has them The spools should have .0003 to .0005 clearance
Drift in the lift is about 8 inches in a hour, Drift in the tilt under power with a bucket attached about a inch in 2 minutes. I replaced the complete hand pilot controller for the lift and tilt and the manual lowering valve. Holding poppets I presume that would be the spool valves on the main valve?
I don't think the controller would be the porblem all that it should be doing is taking the spools off center when you apply pilot pressure. Yes those would be on the main valve. If you get a parts diagram before you take it out you may not have to take it out so you can see what is what
Try plugging the ports in the tilt cylinders and then see if they move about 1" or so. If they move the piston seals are bypassing, despite the fact you have rebuilt them.
This is a good way to check for cylinder seals.
Impossible for piston seals would not be 8" of drift
Well I have changed all the relief valves on the main valve I even changed the main relief valve. Still no change the hydraulics lift and tilt still drift. I believe I am running out of things to change.
Not that it will make you feel any better but ours dose the same thing.
Valve section could have a anti cavitation valve that is stuck open or the seat damaged. This will cause a gravity leak down. Also not likely but a scare in the bore where spool rides could have gouge connecting Cly. Port and return. Tried to look it up on my cat page but would need serial number.