Cheap 2ton floor jack cylinder question

[alfadan]

I have an "AC Delco" trolley jack that leaks at the ram under a load. I thought I'd tear it apart to see if a new 22mm oring on the cap nut would fix it. When I looked in the bore, there are two identical scorings parallel to each other and the same length at the end of the piston stroke.
These can't be purposely put there, can they? They seem awfully uniform to me.

 

[paulsomlo]

Those are probably a cheap method of providing over extension limiting - the seal hits that area and fluid bypasses.

 

[alfadan]

That must be what it is, being at the end of the stroke. I'll proceed with this fool's errand and update.

 

[jayemm]

Where does the fluid bypass to. Single acting cylinder, the cylinder is extended and already filled with fluid so the fluid can't bypass backwards. If there isn't another seal at the rod end (some cylinders don't) the fluid leaks out past the rod. I'm having trouble visualizing this.

 

[dscheidt]

Where does the fluid bypass to. Single acting cylinder, the cylinder is extended and already filled with fluid so the fluid can't bypass backwards. If there isn't another seal at the rod end (some cylinders don't) the fluid leaks out past the rod. I'm having trouble visualizing this.

Out the end of the cylinder, making a mess. Generally the person pumping the jack notices and stops. if they don't, welll, they make a bigger mess. Either way, the jack isn't over extended, and because the cylinder is full to its normal maximum, the load can be lowered.

 

[alfadan]

It appears that when the seal gets to those cuts, fluid leaks out the top of the cylinder through a couple holes in the end cap, back into the reservoir around the cylinder.

Anyway, the oring didn't work. Might be due to scoring on the rod or it was too narrow. Not worth persuing it more, but worth a shot I guess.