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How to relieve hydraulic pressure?

How to relieve hydraulic pressure?

RE: How to relieve hydraulic pressure?

Are G1 and G2 for the steering maybe?

RE: How to relieve hydraulic pressure?

Impossible to tell based on that diagram. Most of the items mentioned appear to be pressure regulation / flow regualtion / relief setting for the various hydraulic lines.

What the buttons / solenoids do on top isn't noted and seem to be a mystery.

Needs the hydraulic diagram I'm afraid.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: How to relieve hydraulic pressure?

What do you mean by "manually"? Do you mean relieve the hydraulic lock on the system and then put a 36" pipe wrench on one of the wheels and start pushing and grunting to make the wheels turn? Or do you intend to apply a hand pump to one of the ports and make it turn that way? Or are you asking where do you stick a paperclip to hotwire it and make it turn, based on bypassing the controls that are 40 feet in the air?

We need a little more information.

Do you have a model number? Try to search for the instruction manual or service manual for that particular model of lift. You will need both the electrical diagram as well as the hydraulic diagram for us to be able to help you.

Engineering is not the science behind building. It is the science behind not building.

RE: How to relieve hydraulic pressure?

Thank you all for the help. My expertise is electrical but I see there is such a thing called a hydraulic diagram. JLG 1432 lift, service manual doesn't explain how to relieve pressure.
When button to turn right pressed the wheels turn right but pressing left won't do anything. Replaced solenoid from a machine that works but problem remains. So I am hoping that removing hydraulic pressure will enable me to turn column left by hand, if that works then I know something is not seized and can go to the next step.

Steer valve marked

Hydraulic diagram and Closeup of steer section

RE: How to relieve hydraulic pressure?

Adjust the steer relief valves to minimum setting and you may be able to force the steering to move. In messiest way to test, remove both steering relief valves.


RE: How to relieve hydraulic pressure?

The relief valve trick may work. It depends if it’s possibly to relieve all the spring pressure with the adjuster screw.

Another option would be to swap places between the steering valve and the lift valve. The lift valve has float in center making the steering cylinder pressureless. The wheels could then be turned without loosing oil.

The lift should be lowered first as this may possibly cause creep.

RE: How to relieve hydraulic pressure?

If it turns right but not left and you've tried a new solenoid then my best guess is that the relief valve which looks like it is internal to the box is leaking on the left hand line.

Perhaps swap those valves marked steer relief and see if it turns left but not right!

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: How to relieve hydraulic pressure?

Swaping the hoses will accomplish what LittleInch is mentioning. If after swaping hoses to the C! and C2 ports on the valve (they chould be marked) the left works but the right does not (which used to work), then the problem is most probally in the valve. A New spool or solenoid might required. Note there is another solenoid on the Opp side of the valve. Could be the spool n the valve. If the Right still works then it may be in those reliefs or the seals in the cylinder. Cracking a fitting (if 3000psi or under) will relieve pressure, but you need to be carefull as it can get messy. I wrap a rag around the fitting first. And put a bucket under the fitting. And have a fiiting cap ready to plug the line so gravity does not dump fluid on the ground. Or have a helper hold the 2nd line in the air while while your moving the first line.

You can check solenoids by removing them and putting a screw driver in the solenoid an pushing the button. You will feel a pull. I am not fully sure this method will work with those solenoids.

RE: How to relieve hydraulic pressure?

I am about to apply the suggestions.
I studied the basics when taking electrical engineering long ago. Not looking to do an entire course just an hour or so is all I can spend learning. If anyone knows sites that explains how to read hydraulic diagrams please tell me.
Service manual is written for someone familiar with these machines so it often lacks details I seek.

RE: How to relieve hydraulic pressure?

I tried to do some things but the connections are too tight, I put some oil to loosen it, will keep trying.
So I disconnected the steer lines at the cylinder, they cannot be swapped as they put different connector types, perhaps to prevent crossing. Now the steer can move either way manually.

While I wait for the oil to loosen things can I test the valves/solenoids since that is most likely where the problem is?

What will happen if...I power it up and push the steer buttons? Will oil spray out from the hoses I disconnected earlier at the cylinder end? I could let it shoot into a container, also push the button just for a fraction of a second.

RE: How to relieve hydraulic pressure?

You can severely injure or kill yourself if you don't know what you are doing. It's not a certainty, but hazards can come from unexpected sources.

Have a read through https://www.hydraulicspneumatics.com/maintenance/f... and consider hiring a qualified service provider. What you are looking to do doesn't require significant skills, but it's probably not a good choice for a first solo project.

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