What is the definitive sighn symptom and diagnostic for cylinder piston seal wear and failure?
- Thread starter CalG
- Start date
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LD1
Epic Contributor
If a cylinder drifts on its own in the EXTEND direction it "could" be piston seals.
Any cylinder drift warrants further investigation...but drifting in the retract direction can rule out the cylinder because the internal leakage is somewhere other than the cylinder.
Some symptoms would be weak power or slow functions.
To further test it is easiest to do with the cylinder unpinned from whatever it is moving.
Extend the cylinder ALL THE WAY. Then disconnect the rod end hose, and try to extend the cylinder even more. If oil comes out the port you disconnected the hose from......your seals are leaking by in the cylinder.
You can do the same test by retracting the cylinder all the way, unhooking the base end hose, and trying to retract even more and see if oil comes out.
Basically by doing this....you are putting FULL system pressure on one side of the piston only....and seeing how much oil comes out of the non pressurized side of the piston. You cant do that with the non-pressurized side's hose hooked up. Because any oil that is bypassing the piston simply returns back to tank and you cannot visibly see what is going on or how much (if any) is leaking by
Any cylinder drift warrants further investigation...but drifting in the retract direction can rule out the cylinder because the internal leakage is somewhere other than the cylinder.
Some symptoms would be weak power or slow functions.
To further test it is easiest to do with the cylinder unpinned from whatever it is moving.
Extend the cylinder ALL THE WAY. Then disconnect the rod end hose, and try to extend the cylinder even more. If oil comes out the port you disconnected the hose from......your seals are leaking by in the cylinder.
You can do the same test by retracting the cylinder all the way, unhooking the base end hose, and trying to retract even more and see if oil comes out.
Basically by doing this....you are putting FULL system pressure on one side of the piston only....and seeing how much oil comes out of the non pressurized side of the piston. You cant do that with the non-pressurized side's hose hooked up. Because any oil that is bypassing the piston simply returns back to tank and you cannot visibly see what is going on or how much (if any) is leaking by
LD1
Epic Contributor
Good video. They take it one step further and do a test at mid stroke as well. This requires a plug for whatever size port is on the cylinder. And most people done have a handful of various plugs on hand to do this test. This is only beneficial if you have a scored cylinder or a ballooned cylinder somewhere along its length of operation that might otherwise test fine on either end. But usually by the time someone suspects a problem....its too late and and the bypass test at either end is sufficient because whatever scoring or ballooning in the middle of the cylinder will have already chewed up the seals and the symptoms will be evident at either end as well.
Notice though on the mid point test...he plugs the base end of the cylinder and applies pressure to try and retract the cylinder. But if the seals are bad.....the rod will EXTEND. And if the seals are good NOTHING happens. Because the oil has no where to go. Same concept as to why a cylinder wont drift in the collapsed direction even if the seals are bad
Vigo327
Platinum Member
I came here to type the 'hold the valve in the retract direction for a long time and see if cylinder starts extending' thing but it looks like it's been covered. Good stuff so far!