743 hydraulic problem

[Joby]

Can anyone advise me on my problem: My 743 lift arms drop slowly on their own, it takes about a minute and a half to fall from full height. I replaced the lift cylinder seals as this was my obvious conclusion, but it is still the same. since re-assembly I have checked the cylinder seals for by-pass (something I should have done before replacing them) but they are fine. The pedal linkeages are all free and seem to operate the control valve effectively. I can raise the lift arms with a chain block with the controls in neutral which seems to indicate a problem with the float control. any suggestions would be appreciated as I don't want to pull the control valve out and strip it down if it's OK. Many thanks in anticipation. Joby

 

[Tazza]

Thats a pretty major leak down. Can you try jumping in the machine, lift the arms. Turn the engine off. As the arms fall, push your heal back slowly and see if the arms stop at any point. If they do, i believe its your load checks by-passing on you. If you have replaced the cylinder seals I'd be pretty sure it is the load checks or lift arm relief valve if it has one fitted.
See if that changes anything and if it does, let me know and i will explain what you need to do, you should be able to do it without pulling the control block.... but not too sure, access will be tight.

 

[Joby]

Thats a pretty major leak down. Can you try jumping in the machine, lift the arms. Turn the engine off. As the arms fall, push your heal back slowly and see if the arms stop at any point. If they do, i believe its your load checks by-passing on you. If you have replaced the cylinder seals I'd be pretty sure it is the load checks or lift arm relief valve if it has one fitted.
See if that changes anything and if it does, let me know and i will explain what you need to do, you should be able to do it without pulling the control block.... but not too sure, access will be tight.

Thanks Tazza, I did some more investigation and found that the problem was a failed 'O' ring in one of the releif valves situated at the rear of the control valve, and like you say it's a bit difficult to get at. I appreciate your advice though and will keep it in mind for possible future reference.

 

[Tazza]

Thanks Tazza, I did some more investigation and found that the problem was a failed 'O' ring in one of the releif valves situated at the rear of the control valve, and like you say it's a bit difficult to get at. I appreciate your advice though and will keep it in mind for possible future reference.

The relief valves you are talking about are actually called load checks. I had this problem in a 731 i had, the O rings and backup rings were shredded causing the arms to drop.
Glad it was simple to fix, but as you found out, a pain to access!