Re: Hydraulic valves?
If cylinders are drifting in (retracting), there is an easy way to see whether the issue is in the cylinder or the DCV.
You said ramS plural, so I'll describe it for 2 parallel cylinders (e.g. TLB Loader Boom)
1. raise the implement and support it mechanically (another machine, shop crane etc)
2. de-energize system (cycle controls)
3. disconnect hoses from the rod end of each cylinder. Plug the hoses or lines, but leave the fittings on the cylinders open to atmosphere
4. unsupport the load (i.e. lower the crane down until the chains are slack)
As the cylinders drift in, watch the two open ports on the cylinders. If oil is coming out of the left port, the problem is inside the left cylinder. If oil is coming out of the right port, the problem is in the right cylinder.
If the boom is drifting down, but oil is coming out NEITHER port, then the problem is in the DCV.
Components inside a cylinder that can cause drift: piston seals, score in barrel, loose piston retention to rod, static seal between piston and rod on some cylinders.
Components inside a DCV that can cause drift:
O ring on Port relief valve
port relief valve
lockcheck(aka pilot-to -open check)
Scored spool in DCV
Spool linkage bent, seized or otherwise causing spool to not be centered in neutral (stir sticks, coffee cups etc)
Things that CANNOT cause drift:
Main relief! (never cause of cylinder drift)
Load check valve in an open center valve.. nope - causes a momentary drop but not drift
Pump
