Is bleeding necessary after replacing hose?

frogpond · Jun 28, 2020

I need to replace a damaged hose on my Kubota BT602 backhoe, leading from the block up through the boom. It controls the dump function of the bucket. I'm going to get a new one made up. I've never done this before, and i wonder if I will need to bleed the air out afterwards, and if so, how to do it. Any advice will be appreciated.

ptsg · Jun 28, 2020

No need to bleed. Just cycle the functions a couple of times after you replace the hose. It might take a couple seconds for the affected circuit to react but it's just taking the air out.

Check out the hydraulic fluid level in the end.

frogpond · Jun 28, 2020

PTSG, thank you!

davedj1 · Jun 28, 2020

And here I thought you were talking about blood...LOL I say yes it is , not air out of the lines though, they should be fine. What I did when I replaced my lines on my woods backhoe is I tied a masons string to the hose before pulling it out, they I had the hose to measure and the string to guide it back in, did it three times out of the 5 hoses and it worked great.

k0ua · Jun 28, 2020

davedj1 said:
And here I thought you were talking about blood...LOL I say yes it is , not air out of the lines though, they should be fine. What I did when I replaced my lines on my woods backhoe is I tied a masons string to the hose before pulling it out, they I had the hose to measure and the string to guide it back in, did it three times out of the 5 hoses and it worked great.

That sounds like a great idea.

frogpond · Jun 30, 2020

And thank you, davedj1. I followed your idea of attaching a line to the old hose to pull the new one through. Totally effective in avoiding bleeding of blood, as well as cursing. As I couldn't find string, I used some wire.

CoyPatton · Jul 1, 2020

ptsg said:
No need to bleed. Just cycle the functions a couple of times after you replace the hose. It might take a couple seconds for the affected circuit to react but it's just taking the air out.

Check out the hydraulic fluid level in the end.

I agree with the no need to do any special actions to bleed the system. But terminology wise I would say that hydraulics are usually a self bleeding system. A couple of examples that you want to eliminate as much air as possible from would be the hydraulic filter (filled it as full as possible when replacing) and any thing to do with the suction/supply line going to the hydraulic pump. The filter is often in this line. Air going to the pump can (highly likely) can cause captivation. This can quickly destroy your pump.

davedj1 · Jul 1, 2020

frogpond said:
And thank you, davedj1. I followed your idea of attaching a line to the old hose to pull the new one through. Totally effective in avoiding bleeding of blood, as well as cursing. As I couldn't find string, I used some wire.

I'm glad it worked out for you :thumbsup:

sparc · Oct 6, 2020

I recently changed a line to the boom cylinder and afterwards the boom now sags under it's own weight. Never had a problem with this cylinder until I changed the hose. Now, even after a few hours of use it has not self-bled and returned to normal. I have down pressure and I can also raise the boom, it just will now no longer stay raised.

And to top it off I have the same symptom in one of the outriggers but in reverse, and I never touched any of the hoses on that cylinder. I can lower the outrigger by gravity I'm guessing but have no down-pressure to lift and level the machine. And I have very little pressure to raise the outrigger. It's like the cylinder is full of air but I never broke a line or any connections on that circuit.

I was wondering if air is in the valve body as the controls are a high point in all the circuits. But the left outrigger, dipper, and bucket all work fine with plenty of power.

Any ideas? I need to get this thing back to work before it gets cold here. I've got work to do for my brother-in-law on his property digging up 10 tree stumps for him and I don't want to be out there in the cold. I hate the cold.