I have a JD #7 backhoe (mounted on a JD 755 c. 1987) that for years the boom would lower slowly as I was using other attachments (e.g., the loader bucket) and I would have to pull it up occasionally with the control. Recently while working it hard removing large rocks the boom failed to raise at all without me physically helping it (even with no load). The rest of the backhoe worked fine (bucket & extension). I had the boom cylinder repacked with JD kit. When I put it back together and bled the lines it still would not lift the boom, yet when I use the boom cylinder in the opposite direction it works fine. In fact, in the opposite direction it will lift the tractor off the ground with ease and the other cylinders (extension & bucket) continue to work fine. Anybody have any ideas what might cause the boom cylinder to work fine in one direction and not work in the other even though it has been repacked? Thanks.
Backhoe JD Backhoe Troubles
- Thread starter EdMaine
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Tractors4u
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Could it be the control valve? Reverse the lines on that cylinder and see what happens.
OkieG
Veteran Member
<font color="blue"> for years the boom would lower slowly </font> ...and... <font color="blue"> the boom failed to raise at all </font>(probably) describes two separate issues. The only one that's definitely a problem is the boom failing to raise. Like T4U, I think the valve is a good place to start.
<font color="blue"> what does fixing the control valve involve? </font> If JD sells a rebuild kit, either they or you could do it. If they don't sell a rebuild kit, it would likely be "iffy" for a local hydraulic shop to be able to find parts. It would still be worth a try. Buying a new valve might be the easiest and quickest way to get back up and running, though probably not the cheapest.
OkieG
<font color="blue"> what does fixing the control valve involve? </font> If JD sells a rebuild kit, either they or you could do it. If they don't sell a rebuild kit, it would likely be "iffy" for a local hydraulic shop to be able to find parts. It would still be worth a try. Buying a new valve might be the easiest and quickest way to get back up and running, though probably not the cheapest.
OkieG
I want to thank you again for your suggestion. I finally got time to work on the backhoe yesterday and tried your suggestion--it worked slick. With the hydraulic lines reversed the problem was reversed. Now I need to decide if I want to tackle fixing the control valve. As you probably already guessed, I am an amateur backyard mechanic. Do you have any suggestions about what not to do or do as I proceed? I have ordered the JD service manual (in CD format) for the #7 backhoe. Ed
BigEddy
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First thing to do is go on JDparts.com and look at all the pictures. It'll give you a good idea of what you're getting into, and what parts are involved. Sounds to me like worn seals (O'Rings) allowing leak-by. I like to review the drawings to decide if it is something I want to tackle, or if it is something best left to professionals with specialized equipment. Personally - I like playing with big heavy bits better than little fiddly things, but that's just me.
BigEddy
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I took a quick look on JD Parts. (I have the same backhoe - so may have to do this sometime in the future) I'd say the problem is either one of the O'Rings on the spool, or the relief valve. There is a seal kit PT8140 available that is $24CDN that has most of the seals required for a valve rebuild. There is a second kit ($297) available that has almost everything internal to the valve, including the relief valves etc.
Depending on your like or dislike for fiddly jobs, looks like seal replacement should be reasonably easy to do. Not sure if you will be able to work on it in place, or if the whole valve assembly will have to be removed first.
Depending on your like or dislike for fiddly jobs, looks like seal replacement should be reasonably easy to do. Not sure if you will be able to work on it in place, or if the whole valve assembly will have to be removed first.
I wanted to follow-up and again thank everyone for their help. I also wanted to let you know how things turned out. After starting to take the hydraulic controls apart, I decided it was more than I wanted to tackle. It went to JD dealer for repair. Turns out the relief valve in the spool was broken in half. Tech at JD said in 23 years he has worked on these, he never saw one split in half this way! Glad & sad I went this way -- glad because I think it would have taken me a long time to figure what was wrong & fix it -- sad when I saw the bill! ...Ed <font color="green"> </font>
