hydralic jack for RV

dewy

Member
my father came to visit me in a camp ground an over extendedthe 4in jack while leveling 40 ft camper..would not go back up...we got some steel under it and dropped camper on to jack with hydraulic line off an got it to go back in at 3in,s at a time.......only has 1 line on jack, no return to pump...whats the difference between cylinders with 2 lines verses 1 line...only name we can find on cylinder is beaverdam W?-53916......4in x 21...where to find one an whats the difference...................thanks as always.......................dewy
 
4in x 21...?

I have never saw a single hose hydraulic cylinder with a 4" shaft and 21" stroke before..
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Single hose cylinders mostly work off of electric motors and solenoids.

Basically the systems open one solenoid to pump fluid into the cylinder extending the shaft/piston and then another opens to pump the fluid out of the cylinder and back into the reservoir retracting the shaft/piston. Most of the problems with these units can be traced to bad solenoids and pressure switches. Then the motor. One extending beyond its capability most often is caused by a bad solenoid or limit switch.



Two hose systems mainly operate using lever operated control valves (tho some use solenoids to open and close the ports). Shove the lever forward fluid is pumped into one side of the piston to extend the cylinder. Pull the lever back and the fluid is then pumped to the other side of the piston retracting the cylinder.
 
The difference between a one line and a two line:

A one line cylinder is called a "single acting cylinder". It provides power in one direction only and depends on gravity, or a spring, or some external force to return it. The fluid goes in and out of the same line. Some single acting cylinders do have 2 lines, but one line is only a vent back to the tank.

A two line cylinder is called a "double acting cylinder". It is powered in each direction depending on which end pressure is applied.

Sounds like something is mechanically binding inside the cylinder, a crushed spring, bent rod, broken piston...
 
Sometimes it will help to wipe down the cylinder rods with transmission fluid. There is also a dump valve solenoid at the pump. They sometimes go bad. Easy to replace. For a temporary fix to get home, loosen the hose at each cylinder and let the pressure off. It is not EPA approved and makes a mess on the ground. Then the "jacks down" warning will keep blasting away unless you top off the reservoir for the jack system. We had to do this a few months ago on our last trip for 2018. Now it is inside and I have all winter to replace the solenoid.
 

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