Why Is My Jack NOT Broken - It Should Be

A few years ago the 12 ton air over hydraulic on my smaller hydraulic press started spraying air and oil while i was using it. It kept working, but it was a mess.

Today I decided to take it off the press and check it out to see if I can fix it. Other than being low on oil there was nothing wrong with it. It worked. It didn't leak air or oil at all much less spray it and make a mess. It just worked.

I considered maybe it was low on oil and somehow that allowed it to not leak, but that doesn't make sense. I topped it off anyway. It WAS pretty low. Maybe 1/2-1/2 down. No change after topping it off.

Why? What was wrong with it that self fixed. I want to put it on the new tuber bender, but I'm afraid if I do that without finding the problem it will fail mid bend and soak me and the tube with hydraulic oil.

It sounds to me like you are talking about internal bypassing. I don't really have an issue with that as long as it has enough force during the stroke. Other than having to take hte jack apart its not a difficult fix either. Just replace the seal that's leaking internally. probably should have clipped that from the video.

That is not what I described, but just to assuage your concerns I'll respond anyway. It exhibits no sign of sag until it is almost to the very top, and the handle does not droop when used manually. I can pump it slightly higher by hand, but then it sags back to the exact same spot. It feels to me more like there is a relief port that prevents it from being pumped to the maximum hard stop. Even if I am wrong that is still not situation I described.

What we have here is a case of answering a different question than the one that was asked.

What was actually described. It sprayed air and oil externally making a mess. Like there was a hole in it, except I wasn't facing the side the media was coming from at the time, and I kept my hand on the valve because it was still pressing the part I needed pressed. Then I disconnected the air and walked away finishing whatever project I was working on at the time. I haven't used it since. It was light pressing. Light enough I have pressed similar projects since then on the arbor press. Admittedly I have a modestly strong arbor press.

What was the likely cause that it was spraying air and oil EXTERNALLY before, and how did it self repair so that it is not doing so now? For those not familiar the air motor does use and vent a lot of air, but it doesn't spray oil.

One answer (only answer really) on YouTube video comments was, "lift something heavy and it will show you." It has springs and I did more testing than was in the video. I don't think so, but this is a valid "smoke test," so the next time I play with it (today or tomorrow) I will do that test. I can't rule out that it needs more counter force to exhibit the problem until I give it more counter force. I'll probably lift the front of my 3/4 ton truck and see.

It sounds to me like you are talking about internal bypassing. I don't really have an issue with that as long as it has enough force during the stroke. Other than having to take hte jack apart its not a difficult fix either. Just replace the seal that's leaking internally. probably should have clipped that from the video.

That is not what I described, but just to assuage your concerns I'll respond anyway. It exhibits no sign of sag until it is almost to the very top, and the handle does not droop when used manually. I can pump it slightly higher by hand, but then it sags back to the exact same spot. It feels to me more like there is a relief port that prevents it from being pumped to the maximum hard stop. Even if I am wrong that is still not situation I described.

What we have here is a case of answering a different question than the one that was asked.

What was actually described. It sprayed air and oil externally making a mess. Like there was a hole in it, except I wasn't facing the side the media was coming from at the time, and I kept my hand on the valve because it was still pressing the part I needed pressed. Then I disconnected the air and walked away finishing whatever project I was working on at the time. I haven't used it since. It was light pressing. Light enough I have pressed similar projects since then on the arbor press. Admittedly I have a modestly strong arbor press.

What was the likely cause that it was spraying air and oil EXTERNALLY before, and how did it self repair so that it is not doing so now? For those not familiar the air motor does use and vent a lot of air, but it doesn't spray oil.

One answer (only answer really) on YouTube video comments was, "lift something heavy and it will show you." It has springs and I did more testing than was in the video. I don't think so, but this is a valid "smoke test," so the next time I play with it (today or tomorrow) I will do that test. I can't rule out that it needs more counter force to exhibit the problem until I give it more counter force. I'll probably lift the front of my 3/4 ton truck and see.

Again I don't think its bypassing internally except at ONE (1) spot near max travel. Symptom previously described. If it were given its under constant spring compression, it would have leaked down atleast a little over night which it did not.

My hydraulic floor jack does bypass a little internally, and it only takes an hour to leak down under just its own weight. It jacks up just fine, and I always use jack stands (or blocking) when I am working on something anyway.

It acts like a relief port at that height and the only difference is that the manual stroke is longer than the air motor stroke.

I know a relief port seems unlikely on a cheap import hydraulic jack, but its a dead cheap feature to have. Anyway, it acts like it.

It's gotta be in the pump section since that's the only part that has both fluid and high pressure air ... Was it intermittent , timed with the pump strokes , or a steady stream ?

Again I don't think its bypassing internally except at ONE (1) spot near max travel. Symptom previously described. If it were given its under constant spring compression, it would have leaked down atleast a little over night which it did not.

My hydraulic floor jack does bypass a little internally, and it only takes an hour to leak down under just its own weight. It jacks up just fine, and I always use jack stands (or blocking) when I am working on something anyway.

It acts like a relief port at that height and the only difference is that the manual stroke is longer than the air motor stroke.

I know a relief port seems unlikely on a cheap import hydraulic jack, but its a dead cheap feature to have. Anyway, it acts like it.

HF has a parts break down in their manual. Though the "air motor" seems to be a unit with out any break down...

The Vevor 20 ton unit on my 12 ton (yeah , I know , and I've beefed critical areas up) HF press has a pump section that can be disassembled . Three long bolts hold the stack of parts together .

Well we used it yesterday to lift the front end of a GMC Yukon. My son's girlfriends vehicle needed new brakes. It lifted it just fine. A couple times actually.

I have a roll around floor jack that is better for this application, but I wanted to check the air over jack, and I figured since we had to lift the truck anyway it was as good of a time as any to test the jack.

We wound up lifting the truck a few times, before switching to the floor jack (faster and easier) and it worked just fine. It had two minor issues. It didn't want to easily fully retract, and up on the very last lowering and removal there was a little hydraulic oil on the base, but I could not tell where it came from. I'm not spending any more time on it anytime soon. I'm just going to order a new one to go on the Affordable tube bender. I've already moved the 12 ton press to the scrap metal for future projects pallet out back.