Pressure Relief Valve problem???

[Enginerd]

Hello All

I'm trying to help my brother troubleshoot a fail in the backhoe arm of his '92 JCB 214.

While in use, he lost the ability to swing the boom from side to side. All other rams are working fine (ie he can extend the arm out, etc.) With the machine shut off, he can manually push the boom from side to side. We took out the pressure relief valve and nothing obvious stood out and all bits appeared in check.

If anyone has any suggestions and/or anything we can check it'd be greatly appreciated!

Thanks!!

 

[kennyd]

Welcome to TBN

Since the boom moves side to side with you pushing on it, the the problem is either in the valve itself, or the linkage connecting the joystick to the valve. My money is on the linkage.

 

[Enginerd]

Awesome, thanks alot m8, ill try it in the morning.

 

[J_J]

Is there pressure going to the swing cylinders? Perhaps the cyl, or chain or what ever turns the boom has broken. Do you have a gage in the system? Does the valve go into relief. You should not be able to push the boom with the swing lever in neutral, as flow from the cylinders is blocked.

 

[jinman]

If one of the swing cylinders has blown an internal seal, it may be leaking so much internally that the boom's resistance is enough to cause all flow to bypass. When you stop the tractor or put the joystick in neutral, if the boom still moves easily by hand, you have to think it might be blown cylinder seal. Your boom swing cylinders are in parallel, but the reverse of each other. Because they are in parallel, one blown cylinder's seal will defeat the movement of both cylinders.

You can remove the hoses from the swing cylinders and check for flow and pressure as the joystick is moved. If you plug both lines to a cylinder, it will lock if the internal seals are good. You'll have to check each cylinder individually while leaving the other open because one good cylinder will lock the boom if your put plugs in the ports. I'd plug one cylinder at a time while leaving the other open and see if I could move the boom. Reverse the plugs and try the other cylinder. Whichever one moves, that is the cylinder with the blown seal. You have to make sure the cylinder is full of oil before testing this way and it may be nearly impossible if the ports are on the bottom or side rather than the top. It might require removal of the cylinders. You just have to get a bit creative.

 

[biggerten]

I agree with jinman. In fact, if it weren't for what he was doing with his tractor in his avatar, I'd say he's pretty smart.

 

[jinman]

To quote Bartles and James: "Thanks for your support."

 

[J_J]

Check your fluid level, if it is low, you may have cracked a fitting or a bad hose. Again, the boom should not move with the valve in neutral.

 

[phanracac]

You can remove the hoses from the swing cylinders and check for flow and pressure as the joystick is moved

 

[dcyrilc]

To quote Bartles and James: "Thanks for your support."

Hey Jinman,

What were you doin' in that pic?