Originally Posted by rvgreg
Glad you fixed your problem. How did you originally come to the conclusion that it was the jack and not a problem with the pump or solenoid valve? It just seems to me that if the jack holds the motorhome up (being under a lot of weight) without problems then it should not leak down when retracted and under no weight. If the internal orings leaked by in one direction, it should leak by in the other direction. Am I missing something here?
Here is the easy worded answer. When the jack piston is on the ground, the piston cannot move. If the coach begins to drop the cylinder must be moving. Remember the oil pressure is the same on both sides of the piston and its two o'ring seals. The system is called balanced and the pump must start to change piston position. Unless the piston seals are worn or damaged (due to trash in the cylinder) or other reasons. The under weight the cyl will slip downward while seals are bypassing.
It doesn't happen when stowed because of lack of heavy load. Pump problems only surface when in use, not when stationary. Sol. valves leaking will result in tank level rise. The two rings per piston are round syn rubber and back each other, non directional.