Prince stack valve leaking off

[number9L]

So, been out of town since getting the Prince SV valve and TnT setup installed. When the 3ph is lifted, my BB will leak down about 1/16" per 2 seconds on the tilt cylinder and about 1/16" per 5 seconds on the top link cylinder. I've isolated the cylinders (unplugged the hoses at the QC) and the BB doesn't move when the 3ph is lifted.

I have no visible signs of leaks on any of the hoses or fittings or around the valve body. Guess its leaking off internally back the the outlet or PB port?

Is this a common trait with stack valves? Or Prince SV series valves?

Gonna be frustrating trying to regrade some land this week with the BB position drifting on the move.


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[number9L]

So I've got 3 sets of QCs. I tested with the tilt cylinder in each set of QCs and each time the BB drops 1/2" in 22 seconds. I then tested and had my 2 boys set on the RH side of the BB and it dropped 1/2" in 13 seconds (they weigh about a combined 90#).

Is this amount of leak off to be expected? I can't see all 3 work sections being faulty. Is there something I'm missing somewhere else?

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[medic0648]

Both sections of my sv valve leak also. With the engine running on the jd the loader arms go up and the bucket dumps. The jd is CC though. it actually does a decent job staying in place when turned off though.

 

[J_J]

So I've got 3 sets of QCs. I tested with the tilt cylinder in each set of QCs and each time the BB drops 1/2" in 22 seconds. I then tested and had my 2 boys set on the RH side of the BB and it dropped 1/2" in 13 seconds (they weigh about a combined 90#).

Is this amount of leak off to be expected? I can't see all 3 work sections being faulty. Is there something I'm missing somewhere else?

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Everyone would like a 0 leak down, but it just ain't going to happen. Some valves, cyl, hyd systems are just better than others.

You will have to verify if the 3pt will leak down before the following check is done.

You do know there is a leak down rate associated with each model valve, and it is hard to find the correct answer as to when the leak rate is good enough for a replacement. Might even have to be verified by a dealer.

It could be something like 10 drops a minute, etc. If you got the valve from Surplus, call them and asked what the leak down rate is for replacement.

So if you want to see what the leak down rate on the remote valve is, then raise a load on the 3pt, and turn the transport knob clockwise to lock the 3 pt. and then remove the return/out hose and then let it drip in to a jar/bucket. Time the drops or volume or both.

A heavy load could force fluid past cyl seals and valve spools.

You can use needle valves to isolate cyl and valves.

 

[number9L]

I am going to call Surplus, but am going to start with Prince first. I'm going to ask what the leak down rate is and if they think 1/2" in 22 seconds is acceptable. It's NOT to me. That's nearly 1-1/2" a minute. I spent a lot of money on that **** valve and if that's "normal" and I have to live with it I guess I'll look into needle valves to be able to set the implement in position and lock it in place. Be a PITA working that way though.

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[Leejohn]

That is way to much, maybe over night I could live with.

 

[medic0648]

I can see why I have bypass on mine. Between the tractor being cc running about 2850psi and the bucket cylinders needing to be rebuilt in the not too distant future stuff is bound to creep.

 

[J_J]

medic0648,

If you have a hyd gage on the hyd system, does the pressure stay that high with all valves in neutral, or does it decrease down to a stand down pressure?



In both CC and open center hyd system, and no flow from the pump, the load on the cyl will determine the leak down rate.

The cyl should not be bypassing to measure the leak down on the valve. The amount of the load will also dictate the leak down rate.

Using a CC hyd system, with pump running, standby pressure might give a certain leak down rate and full pressure might give another leak down rate, plus the weight of the load.

What you might not know is where is the valve leaking the fluid to, to base end of cyl, to rod end of cyl, or to return port.

 

[Tx Jim]

I can see why I have bypass on mine. Between the tractor being cc running about 2850psi and the bucket cylinders needing to be rebuilt in the not too distant future stuff is bound to creep.

If your closed center system is operating a 2850 psi that's 500 psi TOO HIGH and it's no wonder you have hyd problems.

 

[Tx Jim]

medic0648,

If you have a hyd gage on the hyd system, does the pressure stay that high with all valves in neutral, or does it decrease down to a stand down pressure?




Using a CC hyd system, with pump running, standby pressure might give a certain leak down rate and full pressure might give another leak down rate, plus the weight of the load.

J_J
There should be very minimal difference in stand-by pressure & operating pressure on a CC system on a JD. Actually except for a brief moment the pressures will be identical.