Backhoe Jinma 354 Jw-03 Backhoe problem

[Slydec]

My backhoe is sick
* at first my boom was raising realy slow and did not raise at all with a load when it was hot. also notice that the other cylinder where week
* i changed the hydro oil because it add some water in it and i brought my boom cylinder to a mecanic to check and change the seal..
* it did not solve the problem but i did buy a pressure gauge
the pressure was 1000 on all 3 cylinder , need at lest 2000 so ....
* i ordered a pump , cbn-310 and the rebuilt kit for the pump , got it 2 days later and did install the new pump and still got 1000 psi ....
* i have check the FEL with the gauge and had around 2800 psi so the gauge is working right..
* I do not have any leak so the last thing that is left is the valve ...I brought that to the mecanic and he told me that everything is ok .. did reinstall the valve with new o-ring on all 12 hose but still 1000 psi and no lift capacity

 

[3RRL]

Sounds to me it's the pressure relief on the backhoe valve. Have your gauge ready and turn the pressure relief valve clockwise ... like you are screwing it into the valve. Check the pressure after every full turn, because it does not take much to get it up to rated pressure.
BTW, if you have a Jinma 354, your system psi should not be more than 2,321psi or 16MPa, I believe. So 2,800psi is way to high IMO. I set all my valves to 2,250psi.

 

[Slydec]

Sounds to me it's the pressure relief on the backhoe valve. Have your gauge ready and turn the pressure relief valve clockwise ... like you are screwing it into the valve. Check the pressure after every full turn, because it does not take much to get it up to rated pressure.
BTW, if you have a Jinma 354, your system psi should not be more than 2,321psi or 16MPa, I believe. So 2,800psi is way to high IMO. I set all my valves to 2,250psi.

I did try that and it did not do nothing (about 200 psi variation from end to end of the bolt)
if you talk about the big nut under and on the right of those 6 valve

Each time i try to raise the boom i ear something sucking air or some sound like that,, i guess that would be the pressur valve ... the same sound as when you have the cylinder raise at it'S max ...
i'm in canada .. is there any quick fix for that or any place to buy that piece because i realy need that BH to work


I'm not to good on hydraulic just started to play with that stuff about 4 weeks ago so.... i'm good with tools but my patience is running realy thine by now

 

[RonMar]

Yep, if it is not building proper pressure on any cylinder when you work that cylinders valve, then either the pump is having difficulty making the pressure, or the pressure relief is relieving early. Since it is a new pump, I would look tothe valve. How/where are you hooking up your pressure gauge? The dealer I bought mine from said the majority of issues he had seen with these hoes were with the valve, and due to crud in the oil/system.

One thing I noticed on my JW/HW-03 hoe is that the way the oil is returned to the tank thru a banjo bolt, makes for a fairly high velocity straight stream into the top of the tank. This straight stream shoots right across the top of the fluid in the tank and forces air into the fluid in the tank. Kind of like shooting a straight stream garden hose nozzle into a bucket of water. This airated oil then flows right across the tank and down the side and right into the suction strainer. My pump had a little bit of squeel untill I added a return line filter and re-did the tank return port. It is now a larger diameter low velocity return into the tank and the pump dosn't make any noise now...

 

[RonMar]

I did try that and it did not do nothing (about 200 psi variation from end to end of the bolt)
if you talk about the big nut under and on the right of those 6 valve

Yes, under the valve block on the right side as seen from the rear of the tractor, should be the relief valve assembly. It is on the same end of the valve where the high pressure inlet line attaches from the hydraulic pump.

I would reccomend that you take a wrench and completely remove the relief valve cartridge and look for some crud in there that may be keeping the valve stuck open. A relief valve stuck open could cause the symptoms you describe, low pressure, and adjustment has little effect on pressure.

 

[Slydec]

Yes, under the valve block on the right side as seen from the rear of the tractor, should be the relief valve assembly. It is on the same end of the valve where the high pressure inlet line attaches from the hydraulic pump.

I would reccomend that you take a wrench and completely remove the relief valve cartridge and look for some crud in there that may be keeping the valve stuck open. A relief valve stuck open could cause the symptoms you describe, low pressure, and adjustment has little effect on pressure.

So you tell me to undo all 4 bolt on each side of the valve assembly and clean everything or juste just undo the relief valve itself . sorry if it's a stupid question but i don't wanna undo something that i should not....

for the Gauge i place it on the end of every hose but mainly on the raise line of the boom

 

[Affordable]

Here is a pic of the relief valve dis assemblied,as you can see there are alot of small parts that can get debris in them.


Tommy
Affordable Tractor Sales

 

[RonMar]

Yes, take out the 4 screws. The relief valve cartridge is held in place on the bottom of the valve block by a 4 bolt/screw flange. Loosen those 4 screws and get the assembly broken free, then remove the 4 screws and slowly lower it out of the valve block. Note how the parts are arranged so you can put it back together the same way.

Directly above the relief valve on top of the valve block is a large plug with a standard screwdriver slot. That is the check valve, and under that plug is a spring and ball. These can also be removed easilly and should allow you to look straight down thru the valve at the relief valve orifice. Just make sure there are no objects in the passages or that relief hole that the relief cartridge fits up into, or hung up on the relief valve assembly itself.

The top face on the relief plunger should also be smooth, as should the valve seat that it fits up against so it makes a good seal. Basically the spring and plunger sets against a valve seat and keeps the oil from passing, till the pressure on top of the plunger exceeds the spring pressure on the bottom that you set with the adjuster nut. If that plunger dosn't seat fully and seal against it's valve seat, it will always allow fluid to flow and the pump/hoe will never be able to build full pressure.

If you are in doubt as to how it should look, or if you drop something and are not sure how it should go back together, I can pull mine tomorrow and take some pictures of it.

Good luck

 

[Slydec]

well today i have clean the pressure relief valve and i did get some pressure back but only to 1800 psi at the max (when the valve is almost fully close)
i got all the piece in the pic on post #7 but one is different. I don't have the one at the bottom right of the pic insted i got a small cylinder and a small spring (forgot to take some picture) anyway my last thing i think i'm gonna do is take everything apart (valve body) and clean everything in there
anybody got any experience on that part or is it a big no no to do that ??
also my oil was getting very hot today during the testing part!!? (oil is AW32)
and i think i have something wrong with my Boom/swing lever maybe thats part of my problem because when i put the pressur gauge on the boom cylinder i see a littel bit of foam when i remove the gauge but not on the other cylinder but i don't see any leak on the hose and everything is tight

 

[Slydec]

Thanks for the help
Problem was 2 busted O-ring on the center part of the relief valve
here some picture of the relief valve (parts are place in order)
and some of the valve body