Will doing this hurt a jack?

[NoSkills]

I'm a modest DIY-er and bought the Harbor Freight 2.5 ton aluminum jack to use for home ATV and lawn mower repair. I chose it because of the high lift height, light weight and reasonable cost. Got tired of blocking up my bottle jack to reach the frames and then having to pump it a zillion times to lift the load 6 inches. It may not be Snap-On but it works great for my limited demands. Since I'm tight on storage space, it gets stored in front of my tool box (with the lift arm extending under the tool box), until I can clean out/re-arrange things. But to get into the drawers, I have to lower/raise the handle, with the relief valve open so the arm doesn't lift.

Will pumping a jack with the relief valve open cause any problems?

 

[shawhite]

Can induce air into the hydraulic system.

 

[malibu101]

Nope. You'll be fine.
Doing that just allows the hydraulic fluid to take another path. No harm at all.

In fact what you describe is the normal bleeding procedure.

 

[Loscaldazar]

Can induce air into the hydraulic system.

If I'm understanding the OP correctly, isn't what he is doing how you generally bleed air from the system? The instructions that came with my Arcan 3.5 ton jack say to periodically pump the jack several times with the handle twisted to the left (i.e. open, so the pad doesn't actually lift when you pump it) in order to bleed it of air. Do it every time before and after I use it.

EDIT: Malibu beat me to it.

 

[Hiball]

No.. it won't hurt anything.

 

[isb cornbinder]

Do not worry about this. The relief valve goes into by-pass to allow the jack oil to return to the reservoir. You will not cause a problem. If any air does get into the system, for any other reason, the air will find it's way out in one cycle of the jack.
Please be careful when jacking stuff up. Never use concrete blocks (aka cinder blocks) to block anything. Use proper jack stands. My friend Bob had a pickup truck fall on him about a decade ago and he has not walked since.