whokares2 said:
2002 Georgetown Dewald leveling Jack's drift down one at a time. I have them tarp strapped up for storage but they still drift down about 2 inches. Is there one check valve I should look for, I can't believe all four legs went bad at one time.
It is a 2002 model so it must have seen considerable miles and use.
Possibly the fluid has never been changed or serviced - though that will not cure the problem at this point, it may have contributed to its development by accumulating contamination over the years.
There is only one reason for the cylinder extending as you describe and that is because fluid is leaving the rod end of the cylinder.
There are only two ways for the fluid to leave - barring external leakage.
1. Out the hose on the rod end of the cylinder and back to the reservoir past the directional control valve spool.
In order to test for this leakage you would have to access the return port from the directional control valve to the reservoir - and I?m not sure that you can do that.
2. Past the piston seal and into the larger volume of the piston end. In this case, fluid will not leave the cylinder because the volume on the piston side increases faster than the volume on the rod side decreases.
You say that they drift down ?one at a time?.
Does that mean that the first one comes down the 2 inches and stops - then the second one starts down - and so on?
Do they do it in the same order every time?
Is the 2? drop accurate and consistent from one cylinder to the next?
In the operation I can see that the cylinder leaking down will move fluid from the rod side of each cylinder to the larger piston end.
Since the smaller volume on the rod side will not fill the expanding larger volume on the piston side the movement will slow or stop all together once sufficient vacuum is generated on the piston end to increase the resistance to extending
Here is a link below that will describe the testing of the cylinder piston seal. The test is on page 13.
It would take about 30-45 minutes or less to test all cylinders. The first cylinder to test is the one that leaks down first or the fastest. Then go on from there.
https://www.gulfstreamcoach.com/media/uploads/1/11486_Dewald-Hydraulic-Leveling-System-Manual.pdf
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