lw6 prv problems

[intheground]

I have a jima 284 with a lw6 backhoe. I believe I have a sticky or dirty prv on the boom lift valve. (when I lift the boom out of the hole, no power and the pump squeals) could someone help me with location cleaning and adjustment of the prv.
thanks

 

[J_J]

Is the pump squealing or the relief valve going off?

 

[intheground]

Is the pump squealing or the relief valve going off?

believe the relief valve is going off. the fluid gets hot

 

[J_J]

believe the relief valve is going off. the fluid gets hot

What else is in the hyd circuit? Could one of the other valves be sticking. Are the other cylinders moving at all. Put all the levers to neutral and jiggle them to make sure they are in neutral, and exercise each cylinder to see which spool is causing trouble. The relief valve going off a lot will definitely heat up the oil, and you want to keep the hyd fluid below 200 preferably around 180 degrees. Maybe the relief valve is stuck open, If possible take it out and clean it.

 

[intheground]

What else is in the hyd circuit? Could one of the other valves be sticking. Are the other cylinders moving at all. Put all the levers to neutral and jiggle them to make sure they are in neutral, and exercise each cylinder to see which spool is causing trouble. The relief valve going off a lot will definitely heat up the oil, and you want to keep the hyd fluid below 200 preferably around 180 degrees. Maybe the relief valve is stuck open, If possible take it out and clean it.

nothing else in the circut just the back hoe . runs off pto pump. the other controls work. just the boom lift given me trouble. when I lift out of a hole no power and can hair difference in pump sound like I was holding it on at the end of a stroke. when I lift the boom it will even start to drop even with the control engaged. oil gets hotter than 180. that's what it seems like the valve is stuck open. could you give me some direction on location and taking it apart. fairly new to hydraulics expect fpr owning a jinma and the usual problems

 

[J_J]

Try this before you take the valve apart, switch the hoses with the bucket cylinder and see what happens. If the problem switched to the bucket, then that spool needs cleaning, if it has o-rings, it can be rebuilt. Most valves are made to close tolerances, and you can not just go and get a spool of the shelf. You might wind up putting a new spool in a worn barrel, etc. I don't know how old your BH is, but a new BH valve set may be required.

This is going a little far, but it is possible. If that valve has a PB port, theoretically, you could add a single valve and plug off the old port to the boom, or shift the boom to one of the other outlets.

 

[RonMar]

I bet the problem will move with the port when you swap like JJ suggested. It sounds to me like the PRV is relieving early or is partially stuck open, or your pump is having problms maintaining pressure when it warms up. YOu need to KNOW what pressures you are dealing with. Untill then it is all a bunch of guesses...

To check the pressure you need to get a metric to NPT adapter and a 0-5000 PSI hydraulic gauge. I think the adapter you need is a 18 x 1.5MM to female 3/8 NPT. You will need a 3/8" to 1/4" NPT bushing and the gauge. If your valve is like the others I have seen it has straight metric to O-ring face seal adapters in all the working ports to adapt to the ORFS hoses the chinese used on these hoes. You can take one of these adapters with you to the hydraulic shop to make sure you get the right metric to NPT adapter for the gauge.

To measure the pressure, make sure all the BH parts than can move are firmly on the ground so nothing free falls uncontrollably when you remove a hose. To do this work all the levers on the valve with the engine off/no pump to make sure no circuit has any pressure on it. Pay attention to where things are at, as people have been killed by hydraulic structures comming down on them when they broke open the hydraulic fitting that was supporting the load. Remove a hose and a metric to ORFS adapter from one of the working ports on the BH valve and screw in the new adapter and gauge. Put the hose you disconnected into a bucket, and be carefull not to loose the ORFS O-ring or sealing washer. With your safety glasses in place, startup the tractor and engage the pump. Try sending fluid to that port you connected the gauge to. If you get it right, nothing will moive and the gauge will stop the fluid from flowing and force the relief open. the pressure you see on he gauge is the pressure the relief is opening at/maintaining. If you send it to the other port, the cylinder in question will move and fluid will come out the hose you put in the bucket Keep doing the test and get the fluid warmed up and look for any changes

The boom dropping a little when you first activate the lever is normal as the control valve on these hoes does not have individual load checks and the boom load can cause more pressure than the system is up to initially. The same thing will happen when you try to lift the boom and work any other lever. The boom will instead go down and he other circuit will work faster than normal as the boom falling feeds extra fluid to the other more lightly loaded cylinder(path of least resistance).