L39 Backhoe problems

[ddbackhoe]

Would you not say that if he can not fully extend the outriggers that something is not right.

Anytime you can not extend a cyl, something is not working right or the design is wrong.

In his first post

The backhoe performs all functions quickly and smoothly, but with no power. The outriggers will pick up the machine easily, but the hoe won't even budge it.

Hence my comment of being down to 2 or 3 spools (boom, stick and/or bucket)

 

[J_J]

Quickly and smoothly doesn't mean squat if he has no power.

I am not sure he is doing the relief test correctly.

If the BH valve can make the relief go off at tractor set relief pressure, then everything should work correctly.

Question is , did he see loader relief relief pressure?

Did he ever see BH relief pressure?

 

[J_J]

Quickly and smoothly doesn't mean squat if he has no power.

I am not sure he is doing the relief test correctly.

If the BH valve can make the relief go off at tractor set relief pressure, then everything should work correctly.

Question is , did he see loader relief pressure?

Did he ever see BH relief pressure?

 

[korydz]

Update:
I had some time to play with it tonight. No solutions yet, but checked a few things and I have a better description of the problem:

-I cleaned and reconnected the three fittings on the hoe.
-I pulled the boom and dipper relief valves out. They look clean and are not stuck.
-I did a pressure test on the main backhoe supply line as described in the WSM. 2500psi at idle and it climbed to 2700psi at full tractor RPM (2700RPM) and did not trip the main relief. I didn't want to over rev the engine, but I think it's safe to say this isn't the issue. Diverter from BH to 3PT work properly.

I tried the hoe again and made some better observations:
-Stabilizers are fine.
-Bucket is fine.
-Dipper retract will audibly activate its individual relief valve when over pressured as you'd expect.
-Boom (both directions) and dipper extend fail.

Here's the detail on what I mean by fail, and I should have been more clear on this before. If I try to lift the tractor with the boom (with the dipper and bucket tucked in), the cylinder will move a couple inches and then fail. It doesn稚 just stop as it would if there was an over pressure relief, it actually drops any of the weight it picked up. There's no sound of a relief, just the change in sound from the tractor from being loaded to unloaded.
More confusion: I was able to get the boom to fully lift the tractor a few times. It seems if I kinda snuck up on it by building pressure slowly, it would "catch" and then give me full power. I wasn't able to replicate this on the dipper.

Do I just have a bunch of gunk in the spools? Is there any big trick to taking them apart and reassembling? Do I need new seals or o-rings or anything? Can I just flush the backhoe痴 hydraulic system somehow? Keep in mind this is a 400 hour tractor in very good condition. It sat for perhaps as long as a year at the dealership. Everything I've looked at seems like it hasn't been touched. No wrench marks or missing fasteners etc., so I'm tending towards issues from sitting rather than abuse or someone monkeying around with it.

 

[J_J]

-Boom (both directions) and dipper extend fail.

When you did that, what pressure did you see?

You could switch hoses on the BH valve and see if a spool is bad.

On the boom spool, you could extend the cyl and then remove the rod end hose and try and extend some more. If fluid comes out the rod end port, the cyl is bypssing.

If the cyl checks good, and you still can't get pump max pressure, then the valve spool is bad.

 

[Egon]

Are the valve linkage controls working properly?

 

[J_J]

Update:
I had some time to play with it tonight. No solutions yet, but checked a few things and I have a better description of the problem:

-I cleaned and reconnected the three fittings on the hoe.
-I pulled the boom and dipper relief valves out. They look clean and are not stuck.
-I did a pressure test on the main backhoe supply line as described in the WSM. 2500psi at idle and it climbed to 2700psi at full tractor RPM (2700RPM) and did not trip the main relief. I didn't want to over rev the engine, but I think it's safe to say this isn't the issue. Diverter from BH to 3PT work properly.

I tried the hoe again and made some better observations:
-Stabilizers are fine.
-Bucket is fine.
-Dipper retract will audibly activate its individual relief valve when over pressured as you'd expect.
-Boom (both directions) and dipper extend fail.

Here's the detail on what I mean by fail, and I should have been more clear on this before. If I try to lift the tractor with the boom (with the dipper and bucket tucked in), the cylinder will move a couple inches and then fail. It doesn稚 just stop as it would if there was an over pressure relief, it actually drops any of the weight it picked up. There's no sound of a relief, just the change in sound from the tractor from being loaded to unloaded.
More confusion: I was able to get the boom to fully lift the tractor a few times. It seems if I kinda snuck up on it by building pressure slowly, it would "catch" and then give me full power. I wasn't able to replicate this on the dipper.

Do I just have a bunch of gunk in the spools? Is there any big trick to taking them apart and reassembling? Do I need new seals or o-rings or anything? Can I just flush the backhoeç—´ hydraulic system somehow? Keep in mind this is a 400 hour tractor in very good condition. It sat for perhaps as long as a year at the dealership. Everything I've looked at seems like it hasn't been touched. No wrench marks or missing fasteners etc., so I'm tending towards issues from sitting rather than abuse or someone monkeying around with it.

You might put the gauge in the failed cyl circuit and see what the work port pressure is.

Check your manual for the work port relief settings.

Did you switch hoses to a known good spool to check pressure.

Was your hyd gauge in the BH circuit when checking out the BH?

Can you list the max pressure readings for each function extend and retract.

 

[ddbackhoe]

Quickly and smoothly doesn't mean squat if he has no power.

Would have been nicer if you read my whole statement

 

[ddbackhoe]

-Boom (both directions) and dipper extend fail.

When you did that, what pressure did you see?

You could switch hoses on the BH valve and see if a spool is bad.

On the boom spool, you could extend the cyl and then remove the rod end hose and try and extend some more. If fluid comes out the rod end port, the cyl is bypssing.

If the cyl checks good, and you still can't get pump max pressure, then the valve spool is bad.

Please check pressures at the cylinders before switching hoses. If not labeled correctly, you could end up with a control mess (dipper in/boom up, bucket out is now in, etc...) Don't overthink the issue, just use a step by step approach and it'll work out better than jumping around.

 

[J_J]

Update:
I had some time to play with it tonight. No solutions yet, but checked a few things and I have a better description of the problem:

-I cleaned and reconnected the three fittings on the hoe.
-I pulled the boom and dipper relief valves out. They look clean and are not stuck.
-I did a pressure test on the main backhoe supply line as described in the WSM. 2500psi at idle and it climbed to 2700psi at full tractor RPM (2700RPM) and did not trip the main relief. I didn't want to over rev the engine, but I think it's safe to say this isn't the issue. Diverter from BH to 3PT work properly.

I tried the hoe again and made some better observations:
-Stabilizers are fine.
-Bucket is fine.
-Dipper retract will audibly activate its individual relief valve when over pressured as you'd expect.
-Boom (both directions) and dipper extend fail.

Here's the detail on what I mean by fail, and I should have been more clear on this before. If I try to lift the tractor with the boom (with the dipper and bucket tucked in), the cylinder will move a couple inches and then fail. It doesn稚 just stop as it would if there was an over pressure relief, it actually drops any of the weight it picked up. There's no sound of a relief, just the change in sound from the tractor from being loaded to unloaded.
More confusion: I was able to get the boom to fully lift the tractor a few times. It seems if I kinda snuck up on it by building pressure slowly, it would "catch" and then give me full power. I wasn't able to replicate this on the dipper.

Do I just have a bunch of gunk in the spools? Is there any big trick to taking them apart and reassembling? Do I need new seals or o-rings or anything? Can I just flush the backhoeç—´ hydraulic system somehow? Keep in mind this is a 400 hour tractor in very good condition. It sat for perhaps as long as a year at the dealership. Everything I've looked at seems like it hasn't been touched. No wrench marks or missing fasteners etc., so I'm tending towards issues from sitting rather than abuse or someone monkeying around with it.

You might put the gauge in the failed cyl circuit and see what the work port pressure is.

Check your manual for the work port relief settings.

Did you switch hoses to a known good spool to check pressure.

He said he is getting 2700 psi at the BH.

Any idea what the work port relief pressure is?