Backhoe Woods BH7500 problem after replacing port relief valve

[aloha]

My Woods BH7500 backhoe developed a leak in one of the port relief valves. So I replaced the valve. To get access to the valve required temporarily removing several of the hydraulic hoses.

The first time I tried to use the BH after replacing the valve, the boom would not pivot to the left (as viewed from the rear-facing position). I could push the boom to the left, with effort, when the control handle was moved to the left-pivot position. Movements all other directions appeared to be correct and at the force normally expected.

The hydraulics are fed off the tractor, a Kubota B7800.

After working the tractor for a couple hours with the BH mounted the BH would weakly pivot to the left, stopping about 45 degrees to the left of centerline. The force was little enough that I could prevent the swing by grabbing the boom with one hand while the control handle was in the left-pivot position.

I assume that my problem relates to the replacement of the port relief valve, and either I have air in the hydraulic system or the new valve is defective. I welcome any comments or alternative suggestions.

If the problem was due to air in the lines, I would have expected the air to have worked out of the system during the time the tractor was running and through exercising the BH functions that were operating normally. The BH manual makes no mention of bleeding the hydraulic lines after replacing the valve.

Any suggestions? Since it has gone from no movement to the left to moving weakly to the left, is my best bet just to keep the BH mounted whenever possible while the tractor is being used for something else, and hope that over time it regains full function? Is there a secret method for bleeding the lines? Is there any way to test the port relief valve without specialized tools?

Thanks.

 

[leonz]

I believe you will find that the relief valve is set too low and is allowing oil to bypass the work port (they do not come preset from the manufacturer) and have to be set with the function fully opened-working) and set at the system temperature with either a pressure gauge and or a flow rater with an over 140 degree oil temperature.

 

[KWentling]

Holding the valve lever for that motion until it strokes all the way and you here the pressure relief open will purge the air out. You may have already tried that but if you haven't, do. It may well be that the port valve is set so low that it is bypassing all the oil.

Kim

 

[J_J]

Are you sure you connected the hoses back correctly? A hyd gage only cost about $13.plus the fittings for a tee connection before the FEL valve or BH valve.

 

[aloha]

I am bumping this up to see if anyone has other ideas. I still am getting only a weak swing to the left. Thanks.

 

[aloha]

I'm following up to report the solution in case anyone else ever has the same problem and finds this thread.
The solution was one of those DUH things. So simple that one feels stupid for not having spotted it immediately, but also relieved that it was simple and didn't cost anything.

When I removed the original port relief valve I did not notice that the O ring was left behind in the hole. So, when I installed the new valve, there were 2 O rings which prevented a good seal from being achieved. The leakage around the extra O ring did not result in any sign of hydraulic fluid escaping and I might never have noticed except the extra O ring came out with the valve one of the times I pulled it out to look for the problem.

 

[tiomar]

I'm following up to report the solution in case anyone else ever has the same problem and finds this thread.
The solution was one of those DUH things. So simple that one feels stupid for not having spotted it immediately, but also relieved that it was simple and didn't cost anything.

When I removed the original port relief valve I did not notice that the O ring was left behind in the hole. So, when I installed the new valve, there were 2 O rings which prevented a good seal from being achieved. The leakage around the extra O ring did not result in any sign of hydraulic fluid escaping and I might never have noticed except the extra O ring came out with the valve one of the times I pulled it out to look for the problem.

Aloha, a friend's backhoe hast he same problem as you describe. I removed two hydraulic lines in order to remove the relief valve. Went to the auto parts store and found a copper washer of the same size. Did not check the thickness of it; however, it stop the leak. After installing valve and hydraulic lines, the backhoe would not turn to the left. I pulled the valve off and did not see an O ring. I did see a flat rubber seal between the pressure relief valve and the outside port. There were no other seals inside the port.

My questions are:
Where did you purchase the relief valve?
Did the new valve come with all "O" rings?
you can send me an email at this address. cid@teamsecurity.net
In advance, i will appreciate on how to fix the problem