BL4690 backhoe cylinder/hose access

[bigbenkubota]

I was digging out a stump, heard a pop, and then no more lift. BL4690 three-point hitch backhoe on a L3710. Hydraulic fluid started pouring out the bottom of the arm.

What is the process for accessing that cylinder? Turn the backhoe perpendicular to the tractor, remove the upper arm/dipper, lay the arm down and pull the cylinder out? Otherwise I don't see how it can come out without laying down the arm (therefore needing to remove the upper arm) and with the main frame/bracket in the way (so turn it 90 degrees). Any other recommendations?

It appears that it might just be (and I hope) its just an old hydraulic line.

Thanks.

 

[bigbenkubota]

You can kind of see in this picture the lower arm that the cylinder goes into. The fluid was pouring out the very bottom where the 6 hydraulic lines pass through:


Here's the stump by the way:

 

[100 td]

Guessing it's the boom hose or cylinder causing the grief. Get a torch and look up the guts of the boom at the cylinder and see if it's leaking, of if you can establish if it's just a hose. If it's a hose, and the hose has not ruptured from external wear, I personally would bite the bullet and replace all hoses going through the boom at the same time, because I expect you'll be doing it again and again otherwise.
Do you have a shed to work in, or park it under a big tree and winch up on the bucket and operate valves to extend the dipper out flat to allow better access? It certainly doesn't look like an easy access job for the main cylinder. YMMV

 

[bigbenkubota]

Where would it be leaking from the cylinder? I think if its either the cylinder or a hose I'd still need to pull the cylinder, right? I'll need the cylinder out to swap out the hose. Just out of curiosity, would I have heard anything if it were the hose?

I definitely agree with replacing all four hoses that go up through the boom.

I can get it under a beam to lift up on. It seems like I need to pull the dipper and bucket off to get it to lay down enough. Right now I've got ratchets to the top of the boom from the ROPS to hold it up. How much can the ROPS hold laterally?

 

[100 td]

Pop could have been hose or fitting or cap or cylinder. Yes I would remove dipper and cylinder, then bottom pin on boom to work on it. No idea on rops strength

 

[100 td]

I'm probably not far from joining you, I've recently blown 3 on the loader and one on the tractor to hoe connection. Slightly different boom layout though. I think my relief may be a bit sticky

 

[bigbenkubota]

Update and hopefully this can help someone else -
I believe the only way to pull the boom cylinder is to lower the arm below horizontal. I also rotated the boom about 90 degrees to the side to work with my location and that also helped to get the cylinder out.

You do not have to disconnect the dipper or boom assemblies. I found that I had a ton of dirt and grease at the bottom of the boom. That coupled with it being frozen made a mass that I had to work hard to get the first hose out.

It was handy to have the backhoe where I could use a strap to lift up at the boom-dipper pivot in order to access the hoses. You want it up to get access but low to get the cylinder in or out.

I purchased all 8 hoses for the backhoe using the Kubota manual:
Boom Components:

• #8 Boom cylinder hose #70050-93779 (goes to the cylinder inside the boom) (68" long)
• #17 Dipper cylinder hose #70050-93784 (goes on the outside of the boom) (75" long)
• #11 Curl cylinder hose 1 #70050-93789 *** (goes on the inside of the boom to the fitting) (79" long)

Dipper Components:

• #3 Curl cylinder hose 2 #70050-93785 (goes from the boom fitting to the curl cylinder) (46" long)

***70050-93789 is not the correct curl cylinder #1 hose. It is 4" too long and has the wrong fitting at the end (male instead of female). When I pulled the hose out I found it to be the same as 70050-93784. I therefore replaced the curl cylinder hose #1, but kept my dipper hoses. They are easier to get to and I now have 4 spares.

This inner curl cylinder hose #1 goes to a fitting inside the backhoe boom. This can be removed by removing the exterior curl cylinder hose, loosing the exterior nut on the fitting, and pushing it into the boom. You need to do both sides at the same time and have one go up while the other goes down as they hit one another if you just push them straight in.

Lastly, check the fittings for where the curl cylinder hoses meet on the boom. Buy new fittings if yours look rusty or bent - they're cheap and you don't want to have to pull it all apart again.

 

[bigbenkubota]

I'm probably not far from joining you, I've recently blown 3 on the loader and one on the tractor to hoe connection. Slightly different boom layout though. I think my relief may be a bit sticky

Definitely deal with those sticky relief valves. You're lucky in blowing a hose as I bent a cylinder when the relief wasn't right.