CalG: Let me try again here
The curl cylinders operate just the opposite as lift cylinders.
Lift cylinders on the loader hold the load by preventing the cylinder from being compressed. In order for the the loader to drift, cylinder rod needs to enter the cylinder barrel. And the ONLY way it can do that is for it to displace fluid OUT of the cylinder barrel. IE: external leak or back through the valve.
BUT, the same logic cannot apply to the curl cylinders, because they are trying to resist tension. They are trying to resist the rod leaving the barrel.
With the forces trying to extend the cylinder....pulling the rod out of the barrel, creates MORE volume inside the barrel of the cylinder. In a good working cylinder, with good gland and piston seals, the fluid on the rod side of the cylinder is contained by those seals. Not allowed to go anywhere, thus no movement.
With faulty piston seals, the oil can simply bypass the piston, and continue to occupy its "space" within the cylinder body, just on the other side of the piston. When you are extending a cylinder, you are creating MORE room for oil on the base-side, than you actually are displacing on the rod side. This will cause a vacuum. Gland seals and QD's are typically not designed to seal against a vacuum. And even if so, vacuum acts more like a "gas" or air, in terms of being "compressible".
So when it comes to having a cylinder "drift".......the biggest thing to look at is weather the "drift" is causing the cylinder to collapse, or to extend. Assuming NO external leaks, and its a simple circuit with just a valve and cylinder......if the drift causes the cylinder to collapse, it 100% CANNOT be the cylinder at fault.
But drift causing extension of the cylinder....could be either. The OP was 100% correct in his troubleshooting. Isolate the valve and cylinder by unhooking the QD's. IF problem is still there.....its the cylinder. IF problem stops......its the valve.
