Loss of Power after changing out Hyd Hose

[hhsco]

Hi, this question is in regard to a Case 580 Super K- maybe not exactly in the scope of TBN but I figure hydraulics are hydraulics to some degree.

Anyways, my brother-in-law got this beast of a backhoe last week. We drove it about 20 miles across the valley to get it home, then took turns digging holes and see how it all worked and whatnot. Seemed to work fine. When we parked it we found that one of the loader's hydraulic hoses was ruptured and leaking a bit. He was heading out of town and asked me to replace the hose. I had to take off what I assume was both the supply and the return hoses to get to the broken hose. Lost maybe a couple quarts of fluid in this process. After I replaced the hoses I added some more hyd fluid till I could see it in the sight gauge on the right side of the machine.

Started her back up and soon began to notice a significant loss of power- the stabilizers were VERY slow to go up and down, I could barely use the boom swing foot controls and the engine didn't seem to want to give me the power and torque I had before, especially when turning. It seemed to briefly return to normal if I jockeyed the loader hydraulics up and down.

So, do I just have a bunch of air in the hyd lines or is this a symptom of something else? If it i just air, how do I bleed it on a backhoe?

Thanks for any assistance.

 

[J_J]

You can bleed most air problems by cycling the cyl's about 10 times.

You might be able to position the cyl so a port is at the highest position and loosen the port and apply a little pressure to force any air out. When you see fluid, the air should be purged, and as you use the cyl, it should get better.

Try installing a hyd gage in the IN port using a tee and make sure your BH is developing the pressure you should have.

 

[Farmerford]

I think you reversed the supply and return hoses when you reconnected them. That's why jockeying the loader valve would help the backhoe.

 

[J_J]

Find your pump and follow the output hose to the FEL valve.

It should go to the IN port of the FEL valve.

The OUT port hose should go to tank/return hose.

PB hose will go to the next valve.

 

[hhsco]

Thanks for the replys!

I don't think I was very clear- jockeying the loader doesn't help the backhoe (actually haven't tried that as it is kinda hard to reach from the backhoe when sitting backwards). Jockeying the loader seems to "rev" the engine and give me the engine power and turning that seems normal as well as to return normal speed hydraulic function to the loader. Still normal conditions for air in the hydraulics?

I don't want to run it a ton till I'm certain that it is a minor problem for fear of damaging the pump or something equally difficult to repair/replace. I will certainly check how I reconnected the hoses (should be identical to the untouched hoses on the other side) but I don't think I messed that up. Very short hoses looped over double to connections directly above them.

 

[Farmerford]

I am confused; you say the supply and return lines are indentical on both sides. Are there two loader valves on the machine?

Crossed lines would behave as you describe. The pump output flows into the tank or exhaust galley of the valve, and on a power beyond valve has nowhere to go unless one of the spools is shifted. Therefore, the pump flow is being released to tank (or just circulates through the pump) through the relief valve that is on the pump. When you move a spool you connect the tank/exhaust galley in the valve to a cylinder, which causes the cylinder to move, and since fluid is now flowing the load on the pump eases, allowing the engine speed up.

If all that is true, the loader controls will be reversed from their normal directions.

And if all that is true, you are putting system pressure into the tank/exhaust galley of the valve, which it is (probably) not designed to withstand; you may damage the o-ring seals around the spools where they exit the valve body.

Steering would also be affected if it is powered by a priority flow from the pump because the priority flow excess (that normally went to the loader, then backhoe) is now under system relief pressure.

 

[J_J]

I am not sure I can agree about the RETURN and INPUT hose crossed.

On a cyl spool that blocks the fluid when in neutral, if you connect the INPUT hose to the return port of the valve, I think you would cause a deadhead situation, and blow the pump, or valve or hose.

The PB port is designed to separate the OUT fluid and main fluid.

The only fluid coming out the OUT port on a valve with PB adapter is the cyl expended fluid.

It would be possible to connect the INPUT hose to the PB port with adapter, and the fluid would flow through the valve and exit the IN port. Not actually sure of the results.