Backhoe Sanity Check

[J_J]

You will not hear anything.

When the relief goes off for each cyl as you extend or retract, , you know the relief pressure has been reached. The BH movements should be constant with no slack.

The cyl action will feel spongy, until the air is out. As you add fluid to the cyl, air is expelled. If air continues to get in the cyl, you need to look further for the cause.

 

[J_J]

caspar3259,

Do you have a FEL on your tractor? Is so, does the FEL cyl act the same?

What I am thinking, is that it would be unusual for all cyl on the BH to be giving trouble. If all cyl are acting up, then I believe the air is coming from the tractor hyd pump via a suction hose.

Cyl can suck in air from the rod seals of worn or well used cyl over time, and will cause some of those things you observed.

With good cyl, and a good valve, the BH should have all the applied power manufactured in to it. It should dig with a certain force and with no slack or floppiness, and lock in place and hold when the levers are released.

It might have restrictors, maybe not. The relief on the BH should be set equal toor below the PRV on the FEL.

A hyd gage should be installed.

 

[caspar3259]

J.J. - thanks for all the info. I have a lot to learn about hydraulics.

Yes I have a FEL and it has been working fine.

The only cylinder on the backhoe that has given me trouble is the dipperstick.

I don't *think* the cylinders feel spongy. When I move the dipperstick and let go of the lever it comes to a quick stop and holds there.

I'm starting to think it is working as designed, but I'll go through the "purge the air" procedure to see if it makes any difference. If anything still seems odd, maybe I can get some video of what I am seeing so you can see what I see...

-Jeff

 

[caspar3259]

Update: I tried the procedure to purge air from the dipperstick cylinder. Afterwards I did not notice any difference.

I'm coming to the conclusion that it's working normally. I think what's happening is the dipperstick cylinder is the "weak link" in the system and can be overpowered by the bucket or boom cylinder. I would guess that the relief valve has a lower PSI threshold than the others, so pressure from the other cylinders can cause the dipperstick cylinder to compress/retract under pressure. When this happens the rod end of the cylinder does not draw in enough fluid, so there is some "slack".

Maybe this is a problem as the boom and bucket cannot exert full force if the dipperstick is moving too easily.

 

[J_J]

Does your BH have work port reliefs? Check them out with a gage. You can put the gage on each cyl and check the pressure and relief it the valve has them.