Hydraulic Jack getting air in it

[Alan H.]

Have a really fine Harbor Freight POS 12 ton bottle jack. It would spring back up when you opened the release valve and pushed it down. Obviously it had air in it.

When I took the fill plug out and it hissed. I pushed the cylinder all the way down, filled with hydraulic oil acquired from the auto parts, and put the fill plug back in. Used it in the past week lifting an Airstream trailer and it worked fine for a couple of lifts and then bingo, SOS. I was pumping it as high as it would go.

Any ideas as to what the problem is? I would like to get this thing fixed since I have at least 30 dollars in it. Seriously, thought about dropping it in the dumpster and buying another one from Lowes but of course it will be Chinese as well but perhaps better quality along with being twice the price.

Shall I drain all the oil and refill? Perhaps the hydraulic oil I put in is incompatible with the high quality Chinese foo foo that was put in it to begin with and it is off gassing some noxious gas??

 

[mech-tech]

1. Fill the jack with hydraulic fluid to the proper level. It is possible to overfill the resevoir on some jacks depending on their design. Refer to the paperwork that came with the jack.

2. Leave the Filler Plug OFF. With the Release Valve OPEN (as if you were letting the jack come down), pump the handle about 20 times.

3. Put the Filler Plug ON. CLOSE the Release Valve. Try to jack up the unit. If it works, you are on the right path. Note....I would do steps 1, 2, and 3 a few times.

 

[mech-tech]

Also if the jack is stored laying down, it will trap air in the system.

 

[phillip-r-s]

I had never heared of this until recently, but try bleedin the air out. Remove the rubber plug in the back top it off with fluid, open the valve, and then pump rapidly for a few seconds, then top off the fluid, replace the plug and try it out.

 

[Hiball]

Does the jack have a proper amount of oil in it? Basically when the jack ram is completely retracted and in the jack is in the vertical position, the oil level should be "at or just below" the fill plug. If your oil level is low, you can get a mixture of oil/air pumped into the cylinder when the reservoir gets low. Outside of that reservoir pressure is normal, which is why you don't completely fill the reservoir because you need head space for air to displace.

 

[Alan H.]

Does the jack have a proper amount of oil in it? ...

Hiball, yes, I filled it up to the level of the plug but I may not have bled it properly by pumping as described by MechTech above. I am going to give it a spin again. I have a lot of fresh hydraulic fluid so i am going to drain it all out first and then put in fresh as well as described here.

Thanks for the responses thus far. I'll come back later tonight when I get a chance to work it over again.

 

[Hiball]

Hiball, yes, I filled it up to the level of the plug but I may not have bled it properly by pumping as described by MechTech above. I am going to give it a spin again. I have a lot of fresh hydraulic fluid so i am going to drain it all out first and then put in fresh as well as described here.

Thanks for the responses thus far. I'll come back later tonight when I get a chance to work it over again.

Its advisable to always bleed a jack, especially on jacks where you have possibly introduced air into the valve system/veins/cylinder account running it low on oil or its had excessive movement/inversion. It might take a couple cycles to rid the system of air, just keep bleeding to you no longer hear air bubbling when retracting the ram from full extension and always check the oil level "during" the bleeding process as any displaced air will be replaced by oil and drop the oil level.

 

[Alan H.]

Okay, it went in the trash. It was getting air into the jack when pumping. Obviously needed a seal on the pump. It was essentially unused but about three years old from HF.

I cleared it out as suggested, filled it with oil again, and used it - SOS. Pulled the plug and it blew air and oil out. So the pump was ingesting air and putting it into the system. I didn't want to mess with it any longer. My time is more valuable than a HF tool!

 

[EDGAR]

Just change the seal on the pump piston and see if this improves the performance of the bottle. This about the only place that air can be introduced while pumping. About the air pressure in the oil tank, that is a common occurrence in all pumps. That is why more expensive jacks have breathers on the oil tank, just to prevent that air pressure build up. Cheap jacks don't get any breathers. Even with this pressure inside, and with good seals, jacks should perform OK.

 

[Hiball]

Just change the seal on the pump piston and see if this improves the performance of the bottle. This about the only place that air can be introduced while pumping. About the air pressure in the oil tank, that is a common occurrence in all pumps. That is why more expensive jacks have breathers on the oil tank, just to prevent that air pressure build up. Cheap jacks don't get any breathers. Even with this pressure inside, and with good seals, jacks should perform OK.

I wouldn't Rule out some Air Ingestion Around the Bottom of the Pump Cylinder if the Lower outer seal is Hardened and its Not tightened down enough, Oil is easier to seal versus Air so Leaks aren't always Prominent. With that Said.. It appears the Current Lineup of Harbor Freight Bottle Jacks don't have the big Oring seal at the bottom that seats in the beveled Area. Without knowing the exact style of the OP's Jack its all speculation I suppose. Just figured I would throw that little tip out there, if someone cant control Air Ingestion with Good Pump seals and Proper Oil Levels. I actually tracked down that Ingestion area with some Soapy water one day after about 30 minutes of bleeding.. Grr.


@OP Its Definitely something simple.. Go get it out of the trash.. LOL. The Majority of Todays Lower Priced Bottle Jacks are operating with the Same components, Unless your going to pony up for a High End Bottle jack, Chances are you will find yourself with a Jack that mimics the One you tossed. The Worst thing you can do with any type of Jack is Put it in the Corner and Forget about it, Id be willing to wager if you pull the Oring seal on the Pump Piston is will be conformed to the Pump Rod and when seals lose there Elasticity they suffer in the sealing department. The Majority of your Bottle Jacks carry a Solid Rubber plug, The Older ones used a threaded plug that you kept closed during transport and opend prior to using. As Edgar mentioned if the seals are in good shape they can overcome the Vacuum that is created when transferring Oil from Reservoir to Cylinder, This is why we don't fill Reservoirs completely, There needs to be some Head space to control this.