BH92 Boom Hydraulics Weak

[OttoOrange]

I have been having so much fun pulling stumps I forgot to update this thread.

The service guy at shop found a restriction in the inlet plate of the first control valve (I assume that was the hydraulic thumb control) causing a pressure drop of 1000 psi. Hence the 1600 psi reading earlier was correct but obviously too low. The plate was replaced and the tractor returned 2 days later. A totally new backhoe experience. I can move the rear end of the tractor around using the backhoe, which wasn’t possible before. I have dug out a stump that was too big to pickup and had to drag it to it’s new resting place.

Thanks for everyone’s input and thoughts. Great forum!!!

 

[edritchey]

Thanks for the update - That's good to hear.

 

[IndMan]

I have been having so much fun pulling stumps I forgot to update this thread.

The service guy at shop found a restriction in the inlet plate of the first control valve (I assume that was the hydraulic thumb control) causing a pressure drop of 1000 psi. Hence the 1600 psi reading earlier was correct but obviously too low. The plate was replaced and the tractor returned 2 days later. A totally new backhoe experience. I can move the rear end of the tractor around using the backhoe, which wasn’t possible before. I have dug out a stump that was too big to pickup and had to drag it to it’s new resting place.

Thanks for everyone’s input and thoughts. Great forum!!!

I know this thread is old but I am having the same issue and I also have the hydraulic thumb. Would it be possible to describe the issue with a little more detail? Was the plate pinching a hose?

 

[TheOldHokie]

I know this thread is old but I am having the same issue and I also have the hydraulic thumb. Would it be possible to describe the issue with a little more detail? Was the plate pinching a hose?

That description is pretty garbled.. Sounds tp me like the restriction was in the linlet area of one of the valve sections.

Dan

 

[IndMan]

That description is pretty garbled.. Sounds tp me like the restriction was in the linlet area of one of the valve sections.

Dan

Thanks for the response Dan, I spoke to Kubota Dealer yesterday and he said that it wouldn't be anything I can see without putting a pressure gauge on the hydraulic system. Today I plan to take it over to him and see if we can solve it. Sounds like a pressure regulator needs to be adjusted.

 

[TheOldHokie]

Thanks for the response Dan, I spoke to Kubota Dealer yesterday and he said that it wouldn't be anything I can see without putting a pressure gauge on the hydraulic system. Today I plan to take it over to him and see if we can solve it. Sounds like a pressure regulator needs to be adjusted.

Your " pressure regulator" would effect everything. The boom circuit has over pressure protection devices that might be defective. That was the first thing thst came to my mind. Hopefully the dealer guys can find the problem and fix it.

Dan

 

[IndMan]

Your " pressure regulator" would effect everything. The boom circuit has over pressure protection devices that might be defective. That was the first thing thst came to my mind. Hopefully the dealer guys can find the problem and fix it.

Dan

Thanks, I wasn't aware of that. I appreciate your help and will follow up after resolving it.

 

[IndMan]

Your " pressure regulator" would effect everything. The boom circuit has over pressure protection devices that might be defective. That was the first thing thst came to my mind. Hopefully the dealer guys can find the problem and fix it.

Dan

They are struggling to find the issue, we definitely have full pressure coming out the back of the tractor and then a drop coming up the boom. I told him about the boom pressure protection device but he was adamant that "it", the release valve was only on the tractor side and the backhoe was all regulators feeding back. Today they plan on breaking down the regulator stack under the shift levers to try and find a leak in the system.

Any other thoughts on this? Also, where is the pressure protection device for the boom?
Thanks for your help on this.

 

[TheOldHokie]

They are struggling to find the issue, we definitely have full pressure coming out the back of the tractor and then a drop coming up the boom. I told him about the boom pressure protection device but he was adamant that "it", the release valve was only on the tractor side and the backhoe was all regulators feeding back. Today they plan on breaking down the regulator stack under the shift levers to try and find a leak in the system.

Any other thoughts on this? Also, where is the pressure protection device for the boom?
Thanks for your help on this.

Tell them to look in the WSM. The backhoe has port reliefs on the boom and dipper stick valves. Here is the parts breakdown. There are two relief cartridges on each valve, items number 750 and 780. Those reliefs are on the cylinder work ports not the inlets and they protect the work circuit from over pressure. If they leak the cylinder will not develop full pressure regardless of the tractor relief - i.e it will loose pressure going up the boom. That may or may not be the issue but if they dont know that they are not as knowledgeable as they think. Might also be why they are struggling.....

Dan

 

[IndMan]

Tell them to look in the WSM. The backhoe has port reliefs on the boom and dipper stick valves. Here is the parts breakdown. There are two relief cartridges on each valve, items number 750 and 780. Those reliefs are on the cylinder work ports not the inlets and they protect the work circuit from over pressure. If they leak the cylinder will not develop full pressure regardless of the tractor relief - i.e it will loose pressure going up the boom. That may or may not be the issue but if they dont know that they are not as knowledgeable as they think. Might also be why they are struggling.....

Dan

View attachment 133386

Dan, thanks for all the info you have provided.

The Dealer did exactly the right thing following his instincts. He tore apart the valve stack under the backhoe levers and found the issue. On the hydraulic thumb valve that was added had some glue residue left from the packaging material. It was just enough to create an air gap somewhere around .001"-.002". That was enough to create a substantial power drop. He used a stone to ensure the faces of each valve machined surface was perfectly flat. It runs great now and I would think this is something that is likely to happen to create this issue.

The Dealer did a fantastic job to correct this and they have earned my confidence and business from this point forward. They were honest, knowledgeable and professional about resolving the problem and conducted themselves like I would expect any Kubota Dealer should. Great Job!