Hydraulic jack troubleshooting

Hey all!

I don't know a lot about hydraulic systems other than some basic fluid mechanics. I have an engine crane, with a hydraulic cylinder. I don't know how hydraulic cylinders work.

As of recently my engine crane/hoist/cherry picker, whatever you call it doesn't lift anymore. I noticed over time it had less lift with each pump I gave it. I didn't see any oils leaking out, so I guess I can eliminate that.

What is causing this? Do I have air in the system and need to bleed it out? How would I do this?

Or maybe the cylinder is just bad, are they easy to replace? I am kind of short on cash and really don't want to buy another entire cherry picker.


Thanks!

If there is air in the lift cylinder it will be spongy. Jack it up so it lifts a few inches and then press on the end of the boom. If it feels springy you may have air in the lift cylinder.

My guess is the pump piston seals are shot.

As for repair, I don't know that you will be able to replace the parts for less than a new hoist will cost you. You may be able to tear it down and rebuild it but I've never done that.

Keith

Is it still lifting, but not as much? If that's the case, you could try bleeding it.

But I would check the relief valve to make sure that it isn't dumping directly to the tank.

Try to see if pressure changes when solenoids are active, if pressure remains the same then relief valve or internal seals are bad.

rootboy said:

Is it still lifting, but not as much? If that's the case, you could try bleeding it.

But I would check the relief valve to make sure that it isn't dumping directly to the tank.

Click to expand...

Yeah it lifts very slowly, then at a certain height it stopped lifting.

Now it doesn't move at all. Ill try bleeding it, anyone know who I would do this?

It's like this, only not this specific brand
http://www.princessauto.com/en/detail/powerfist-2-ton-quick-lift-folding-shop-crane/A-p8210072e

There is a valve or something that I turn when I want to lower it.

It's frigid cold out, but I am in desperate need to fix my truck and swap the engine. Which would probably explain why it's not working too well. I know hydraulics don't work to well during cold temperatures, I have been getting past this by heating up the cylinder with a heater.

I appreciate all the replies.
Thanks

widelto, I believe the OP is dealing with something like this:

http://www.globalindustrial.com/p/m...mpaignId=T9F&gclid=CPHY0oztqcoCFVCAaQod5JAOKA

Keith

Kamenges:

thanks

To bleed air out I used to crack a fitting open and exercise the system. Did that on cherry pickers back in the day. It also spilled a lot of oil, so I'm not sure my method would be allowed today.

In most systems just exercising it will get the air out unless there is a pinhole leak pulling air in somewhere.

Stupid question: hav you verified proper oil level in the reservoir?

It sounds like you are low on oil if it stops lifting at a certain point. On the side of the jack body there will be little rubber plug painted the same color as the body. Pull it out and pour in some hydraulic oil.