I'm working on a d7h that had hydrylic issues in the past. The quick drops seized due to the rods being bent causing the piston to scrape the side walls of the cylinder wall leaving shavings in the quick drop spool. Repairs where made and that was about 500 hours ago now when the blade control is in the hold position and it is up it will steadily go down. If in blade is all the way down and the front of the machine is up the cylinders will hold telling me there is no leakage between the pistons. How do I verify its a quick drop problem and not a problem in the main valve body thanks.
just because the machine can be held up with the cylinders and not leak does not mean in this case that the piston seals or barrel are in good condition. with the cylinder extended and the weight of the machine on the rod it would hold with no seals in the cylinder. if however the cylinder was mounted with the rod facing up and the seals were leaking and you tried to support the machine as you have said it would creep down I would suspect the cylinders first and check them Mark quick drop valve
I agree with Mark. Try isolating one cylinder at a time and run the piston to the end of the stroke. If you remove the pins connecting the cylinder to the blade first it will make it easier. Then remove the return line at the cylinder and try to move the cylinder further in the same direction. If the cylinder is leaking internally you will get oil out of the return line. Repeat the process for the other cylinder.
Thanks i'll try that and let you know
You where right was not a quick drop problem some how metal got into left cylinder and did some serious damage, doing a clean up and replacing complete cylinder assemble thanks
It could have been something related to the previous failure you mentioned in your OP about the bent cylinder rods. If this happens the piston tends to score the barrel and sends metal shavings everywhere.