Backhoe JW-03 Backhoe Problems

[cv63usafsfs]

Hey guys,
I was using my jw03 backhoe today when the boom lift function stopped working. It has been kind of slow in the past and now it has gotten to the point where the boom just sinks down instead of raising up. However after moving around all the other cylinders for a while, the boom will randomly raise back up and then stop working again. Anyone had this problem?

 

[Bob Rooks]

I had a LW-6. Same thing happened to me. Cup seals are blown in the boom cylinder. Is your hydraulic oil kinda dark? If so, the seals have disintegrated. The good news is that the cylinder overhaul kits have urethane (opaque white color) seals instead of rubber.

 

[RonMar]

Hey guys,
I was using my jw03 backhoe today when the boom lift function stopped working. It has been kind of slow in the past and now it has gotten to the point where the boom just sinks down instead of raising up. However after moving around all the other cylinders for a while, the boom will randomly raise back up and then stop working again. Anyone had this problem?

If you put the boom in a position, does it stay there, or does it sink down by itself? IE, will the boom cylinder support the weight of the boom? If it stays in place, I am going to have to disagree with Bob, and say the seals are probably OK. All the other circuits take a fraction of the hydraulic pressure to move compared to the boom up command. The control valve does not have individual load check valves, so when you give a boom up command, the pressure in the main input gallery must be greater than the pressure created in the cylinder by the weight of the boom. Boom going down when you command up(if that is the only command being given) is a classic symptom of low pressure in the main valve gallery. There is a check valve at the valve inlet, under that large standard screw head on the left side of the valve when seated, directly above the pressure relief valve. This keeps fluid from flowing backward into the pump outlet. So if the fluid cannot go back to the pump, where can it go? All this points to a leaking pressure relief valve IMO.

You need to hook up a pressure gauge and see what pressure you are getting. If you search back thru this forum, for this type BH, I posted an article about a little adapter I cooked up using a metric to NPT adapter that screws down in place of that screw head cap above the check valve. Into this you can screw in a pressure gauge to easilly test the pressure that the relief valve is delivering to the system when you load up a circuit...

 

[cv63usafsfs]

Thanks for the replies!
The boom does not sink down until the I give it the boom up command. I am kind of new to tractoring and even newer to this backhoe. It did not come with a manual so I am kind of flying blind as to what the different parts are. Anyone have a labeled picture or something that I could use to figure out what all the parts are and get my bearings straight?

 

[Bob Rooks]

You probably nailed it Ron. Pump or PRV issues. :thumbsup:
I forgot about the sinking boom, which mine did.

 

[J_J]

You might try removing the load checks and cleaning, or the piston seals in the cyl are bad.

Check the relief pressure for correct setting.

 

[RonMar]

You might try removing the load checks and cleaning, or the piston seals in the cyl are are bad.

Check the relief pressure for correct setting.

Simple valve, no load checks. It only has a single checkvalve at the valve block inlet... You pretty much only ever command boom up by itself on these hoe's. Boom up with any other command = boom going down and the other command happening at an accelerated rate fed by the fluid from the heavily loaded boom cylinder backfeeding the system and providing additional flow to the other lightly loaded circuit.


cv63usafsfs What type pump are you feeding this BH with from your JD tractor? what engine RPM are you running? I might have a diagram I can upload tonight, I will look when I get home.

 

[erj]

cv63usafsfs
Send me a PM with your Email address and I can send you a PDF file of the User Manual which contains part breakdowns.
RonJ

 

[RonMar]

cv63usafsfs
Send me a PM with your Email address and I can send you a PDF file of the User Manual which contains part breakdowns.
RonJ

Cool Ron, that was the one I was thinking I have at home, which I got from you

 

[cv63usafsfs]

ERJ I sent you a PM. I don't know the specific type, just that its a PTO pump and not a power beyond from the JD. I usually run it around 10,000 - 12,000 RPM, slightly above idle. I ran into a marine hydraulics guy today at work and ran the question by him. He thought it might be a lack of pressure which is causing the pressure release valve of the cylinder to not function or a stuck release valve. Thats what I was kind of thinking and would explain why just that one function doesnt work but may randomly work when the fluid is cooler. What do you guys think?

 

[Rich Waugh]

Nope, the JW03 hoe doesn't have individual PRVs on each cylinder or valve port - just one PRV for the whole control valve. Yes, you should pull it out and clean it. How does the hoe work if you increase the rpm to say, 1800 rpm?

 

[cv63usafsfs]

I haven't yet run it that high, but ill test it when I get out there. Where is the PRV located?

 

[wdchyd]

Thats what I was kind of thinking and would explain why just that one function doesnt work but may randomly work when the fluid is cooler. What do you guys think?

If only one function is giving you trouble, I'd be changing around hoses to rule-out control valve issue with that one circuit......if the problem doesn't change then check out PRV and/or pump delivery issues....

Sometimes if the circuit you are having trouble with requires the most pressure to do a function then if you have pump problems that one circuit would drop when actuated if the pump can't deliver enough pressure.....

A flow test would determine pump troubles...... Kubota Flow/Load Meter Test - Tractor Videos - Kubota, John Deere, New Holland and More

Pumps that are weak will sometimes fail once they heat up......

IE: if your failed circuit needs 800 psi to function minimally......during a cold start the pump may deliver say 900 psi (and the boom would lift up), after the pump warms up and can only deliver say 700 psi, then the boom would drop when you actuate the control valve......

Maybe I'm not explaining it properly but sometimes pump problems can effect only one circuit if it is the highest pressure needed.......

 

[RonMar]

I don't know the specific type, just that its a PTO pump and not a power beyond from the JD. I usually run it around 10,000 - 12,000 RPM, slightly above idle.

That may be an issue right there. PTO pumps only deliver rated output at rated RPM, in this case 540 RPM on the PTO shaft. To get 540 on the PTO shaft, you need to have the engine RPM up near the PTO rateing mark on the tach. In the case of a diesel tractor, that mark is probably 2300-2400 RPM.

in theory, the pump should be able to deliver full pressure at reduced flow at a lower RPM, but in reality, it dosn't always work like that, as at lower RPM, the speed of the internal pump impellar can allow for more backflow/cavitation...

The input check valve should not allow any reverse flow back toward the pump though, and if the pump is not able to make enough pressure to lift the boom, at the most it should just stay in one place, and not go down. It going down when commanded up still points to fluid leaking by the relief valve.

A quick check to try would be to run the tractor engine up to rated PTO RPM on the tach, and see how the BH performs...

Do you know what fluid is in the BH? If it is still the chinese stuff, I would highly reccomend getting rid of it, flushing the system with kerosene and putting in AW-32 hydraulic fluid. The folks I got my BH from said the only real problems they ever had with these hoes were caused by crap in the oil interfering with spool and relief valve function.

 

[cv63usafsfs]

After I get out of work tomorrow I am going to run a few tests including switching the lines, hopefully that will atleast narrow it down. As for the RPM problem, I have had the hoe since november and have always run it at idle, why has it only become a problem this week? The last owner flushed the lines numerous times and refilled the system with the expensive JD brand fluid right before I got it.

 

[Bob Rooks]

...in theory, the pump should be able to deliver full pressure at reduced flow at a lower RPM, but in reality, it dosn't always work like that, as at lower RPM, the speed of the internal pump impellar can allow for more backflow/cavitation...

Oops.
The pumps are gear type (no impeller) and positive displacement. No back flow at all while running and negligible when stopped, unless it is totally trashed. Gear type pumps will always deliver rated pressure no matter what the r/m, subject to horsepower and relief valve limitations. Only liters per revolution (l/r) or gallons per minute (gpm) will be affected by speed.
Cavitation usually does not occur on the pressure side, this is mostly associated with suction side restrictions.

 

[wdchyd]

The input check valve should not allow any reverse flow back toward the pump though, and if the pump is not able to make enough pressure to lift the boom, at the most it should just stay in one place, and not go down. It going down when commanded up still points to fluid leaking by the relief valve.

??....Input check valve..??....is this something new to tractor hydraulics.....

A check valve can be added anywhere but ......"Input check valve"..??

Post #7 you said this unit has no load check valves also......

I am not familiar with this exact unit so I'm just guessing according to the OP's observations......if there is no "input check valve" and load check valve, and if there is a bad pump (or relief valve), it can drop under load in the right circumstances when it heats up......

 

[RonMar]

??....Input check valve..??....is this something new to tractor hydraulics.....

A check valve can be added anywhere but ......"Input check valve"..??

Post #7 you said this unit has no load check valves also......

I am not familiar with this exact unit so I'm just guessing according to the OP's observations......if there is no "input check valve" and load check valve, and if there is a bad pump (or relief valve), it can drop under load in the right circumstances when it heats up......

The BH valve block on the JW-03 does NOT have any individual load check valves on the individual spool circuits. because of this Some multiple commands do not work well together, and you pretty much can only use the boom up command by itself, as the pressure on that cylinder will overpower any of the other circuits. The valve block does have a single large check valve(spring and ball type) at the input. The fluid comes in from the pump, thru this checkball, passes by the relief valve inlet and feeds on to the main pressure gallery of the valve. That is why I think the problem is most likley a relief valve issue...

Bob, you are correct, gears not impellar, but I have seen pumps fail to deliver full pressure at reduced RPM... Not enough total fluid flow thru the pump to create full displacement or overcome wear leakage inside the pump?

 

[wdchyd]

The valve block does have a single large check valve(spring and ball type) at the input.

Is this typical cuz it's Chinese..??....never seen this before.....

 

[RonMar]

Is this typical cuz it's Chinese..??....never seen this before.....

Don't know if it is typical, but it is a pretty basic chinese valve.