Backhoe Backhoe Drop

[bob1234]

Well, I knew buying used might make for new adventures. My first problem encountered is that the backhoe drops to the ground in about 1-2 minutes. It will do this while the engine running or after the engine is shutoff. There does not appear to be any leaks. How can I troubleshoot the problem to tell if it is the seals or the valve? The BH is a Kubota BT751. Also, if it is the seal, anyone have basic instructions to replace the seals?

Thanks for your help.

 

[Henro]

There may be a better way, but one idea would be to take the hoses off the cylinder, while it is sitting on something to hold it up in the air, like a concrete block for example, and put caps on the cylinder ports. Caps are pretty inexpensive if you don't alread have them, probably a couple bucks each.

Then pull the tractor forward so the backhoe comes off the block (or better use a hydraulic jack, and just remove the jack?) and watch what happens. If the leakage is within the cylinder, the hoe will still fall to the ground. If the hoe does not fall anymore, it is probably the control valve where the problem is.

If it looks like it is the control valve, maybe you could swap hoses between two sections and see if that makes a difference, after connecting the cylinder hoses back up of course.

If the rate of fall slows or stops, then you pretty much prove the control valve section is the problem. If all sections of the control valve are equally bad, nothing would change though...

Just a couple thoughts...there are probably more and better ways to troubleshoot the problem...

 

[Fungus]

I checked my service manual for the BT751. It doesn’t really address troubleshooting a leak down problem.

I think you’ll need to be creative as Henro suggests to isolate the problem.

I don’t see any special tools required for servicing the control valve. For servicing a cylinder the following tools are recommended:

Adjustable Gland Nut Wrench 12010F00720
Slide Jig 12010F00760
Correcting Jig 12010F00770

The BT751 on a B21 is a very nice machine. I have been very happy with mine and wouldn’t let a little problem like this get you down.

 

[v8dave]

With that rate of a drop you could probably hear the fluid with a mechanic's stethoscope. Lift up the bucket, turn off the motor and listen. Take a long screwdriver and place the blade in turn on the cylinder (both ends) and then the valve body. Place the handle tight to your ear and you'll likely hear where the leak is. This is so simple if it doesn't work you haven't lost anything.

 

[bob1234]

Now it gets more interesting. I spoke with the place I bought it from and they told me they were pretty sure it was the cylinder so if I brought in the cylinder they would repack the cylinder. I thought this was pretty good service considering the seal kit is $150.

So, I wake up Saturday and decide to take the backhoe off so I can use the box scraper and remove the BH cylinder and presto, the problem has disappeared. I put the BH to work and it still shows no signs of any problems.

I guess I am going to wait until I put the backhoe back on and see if the problem reoccurs. My only guess is maybe something made it to the valve or seal to hold it slightly open and when pressure was relieved by sitting for a night it worked its way free.

I love problems like these; it's like when the car only makes that funny sound when someone else is driving the car.