Crown 20MT Walkie forklift (lift-lower valve problem)

[J_J]

Yes, you are correct. Thanks

 

[oldnslo]

SoDo,
Not sure how heavy the spring was un the bolt head but is it possible that the pressure created by the load was high enough to compress the spring and allow oil to flow past the O-ring. The way the bolt was installed it would be like a direct acting relief valve.

example: if 1/4" diameter at 100 PSI = 5 lbs force

I guess I have to agree the Cylinder does not appear to be the problem but for peace of mind can you install a ball or needle valve in the cylinder line. This would confirm the cylinder is good a

Check valve should be an easy test. Raise the mast and disconnect the supply line from the pump. No oil flow not your problem.

Manual lower and Solenoid are going to be more difficult. On post #10 you showed the manifold and labeled the plugs. Is there any way to put a plug that you can remove below plug "E" to isolate the cylinder port from the solenoid valve? You could use the same plug to isolate the manual lower valve. This would prevent the cylinder pressure from getting to these valves and should eliminate them one at a time.

Isn't trouble shooting manifolds fun

 

[Sodo]

?.is it possible that the pressure created by the load was high enough to compress the spring and allow oil to flow past the O-ring. The way the bolt was installed it would be like a direct acting relief valve.

The spring is in the same pressure-cavity as the (very light) spring for the hold valve (a ball-check valve). The bolt head is energized like the ball of the check-valve (not the other way around - i.e. relief valve).

I guess I have to agree the Cylinder does not appear to be the problem but for peace of mind can you install a ball or needle valve in the cylinder line.

The line from manifold to cyl is a hard line, and I don't have a hydraulics toybox, no hoses no fittings etc. I would have to get some hoses made up but it's hard to imagine necessary when the return fittings are bone dry.

Check valve should be an easy test. Raise the mast and disconnect the supply line from the pump. No oil flow not your problem.

This is very do-able; I can crack the fitting to the pump. I have NOT done this yet. Such an easy one, thx for mentioning it. I sure wish you guys were here looking over my shoulder.

Manual lower and Solenoid are going to be more difficult. On post #10 you showed the manifold and labeled the plugs. Is there any way to put a plug that you can remove below plug "E" to isolate the cylinder port from the solenoid valve?

I tried to remove plugs B,C,E but they are soft aluminum and the tiny hex was clearly not going to turn it. They have a fairly large thread diameter. The steel fittings had threadlocker and came out HARD. Would have to get the torch out and get serious.

But pretty sure my bolt-plug isolates the solenoid valve. It doesn't isolate the (new) o-ring at the nose of the valve though.

You could use the same plug to isolate the manual lower valve. This would prevent the cylinder pressure from getting to these valves and should eliminate them one at a time.

Isolating the manual valve maybe can be done the same way if I remove the spindle? Or there may be other ways.

Isn't trouble shooting manifolds fun

Well it was fun for a little while but the guys who use it have dealt with it creeping down for 2 years and are about fed up with me saying it's fixable. If course its fixable but I've run out of time and I keep putting more into it because I like a good fight but they are losing patience with me…..

 

[CNC Dan]

It most surly is making a hissing noise, you just can't hear it.

Lift a heavy load an while it leaks down take a wood dowel with a pointed end and bite down on it hard to leave some teath marks. Now touch the end to the solenoid valve. Hear it? No? Try the manual lower valve. Try to do this when its very quiet of course. Earplugs or earmuffs will help.

 

[oldnslo]

Sodo,
The spring is in the same pressure-cavity as the (very light) spring for the hold valve (a ball-check valve). The bolt head is energized like the ball of the check-valve (not the other way around - i.e. relief valve).

Are you saying the nose of the solenoid valve and manual lower valve are connected to the cylinder port. If yes I have been looking at this backwards.

My thoughts on the circuit where.
Pressure connects to "D".
Cylinder connects to "D" through the check valve.
"B", "C", & "E" connect cylinder to top port of manual valve and solenoid valve.
Nose of manual valve and solenoid connect to tank.

If this is wrong I have been giving you some bad advice.

To remove the SAE plugs hit them with a hammer like you are driving a nail. For some reason this loosens them 99% of the time.

 

[Sodo]

It most surly is making a hissing noise, you just can't hear it.

Lift a heavy load an while it leaks down take a wood dowel with a pointed end and bite down on it hard to leave some teath marks. Now touch the end to the solenoid valve. Hear it? No? Try the manual lower valve. Try to do this when its very quiet of course. Earplugs or earmuffs will help.

I have done this before on car engines,,,, but with a flat (not sharp) dowel to my skullbone right behind the ear. Haven't tried the teeth method that's interesting. I'm willing to try anything at this point?. Problem is there's no quiet to be had. Its in a roaring industrial area next to the I-5 freeway? :irked:

But do you think I could be able to hear the difference between 3 valves with an inch of solid aluminum between each valve?

 

[CNC Dan]

I have done this before on car engines,,,, but with a flat (not sharp) dowel to my skullbone right behind the ear. Haven't tried the teeth method that's interesting. I'm willing to try anything at this point?. Problem is there's no quiet to be had. Its in a roaring industrial area next to the I-5 freeway? :irked:

But do you think I could be able to hear the difference between 3 valves with an inch of solid aluminum between each valve?

You might. If you put the dowel on the coil end of the solinoid, or the operating lever of the manual valve. Don't bother on the AL block.

Not having a quiet place is going to hinder your efforts.