BH77 hydraulic problem

[Perfikt]

My dad has a L3901D tractor with a BH77 backhoe attachment. When the backhoe is on and connected it loses hydraulic strength to most everything.

He has tried fixing it by swapping valves and seems to have found a couple faulty control valves. Kubota.ca lists valves, as well as the whole bank of valves.

Is it a bad idea (since they show the assembly around 4k and each valve around 1.3k) to just get and swap the whole assembly? Just start fresh?

The tractor was purchased used and the previous owner used the backhoe for moving around (likely oversized) rocks.

Thanks for any advice, and please let me know if more info is needed.

 

[ayak]

I personally like to swap things that are identical to see if the problem moves. Then I do A-B-A and try to ‘break’ it again. Those are some expensive parts in there.

 

[Perfikt]

I personally like to swap things that are identical to see if the problem moves. Then I do A-B-A and try to ‘break’ it again. Those are some expensive parts in there.

They are, and we have tried the swapping and managed to move the problem around, but there is more than one issue in the valve system from what we can see.

There was initially a boom in problem, so he had the cylinder rebuilt and same problem. Also, the front bucket loses a lot of strength when the backhoe is connected. There are likely leaking reliefs on the assembly (from what we can deduce) and one or more valves actually leaking by internally.

We didn't come to these choices hastily! Haha.

 

[ayak]

There’s a decent YouTube video (actually a few) you can likely find of a fella with what turned out was a relief valve issue in his BH77 that he finally solved. I’d be interested to see if it presents the same way. He persevered after months of torture. Good luck

 

[Perfikt]

There’s a decent YouTube video (actually a few) you can likely find of a fella with what turned out was a relief valve issue in his BH77 that he finally solved. I’d be interested to see if it presents the same way. He persevered after months of torture. Good luck

Yeah, my dad went through a lot of those, tried the different things, some helped but it ended up being intermittent. He's getting frustrated with trying to source it, and has the money to do the full swap, so was thinking that would be the easiest option.

 

[Dave_eng]

If the initial installation (loader or hoe) was faulty (hoses connected wrong) then no amount of parts swapping will fix the issue.

You first need to invest $30 in a pressure gauge and fittings so when you say the loader looses strength with the hoe connected there are some real pressures to consider.

A hose connected wrong on the loader valve's power beyond port will generate grief everywhere.

A complete history of your dad and this tractor is needed. Did he buy it new, was the loader already on it, what model of loader, when did the hoe appear on the scene, was the FEL working fine and then suddenly get weak, any hoses replaced..........

Dave