Loader Bucket bleed down

[thebuildist]

So I put forks on my loader today and it works very well. To satisfy my curiosity, with a pallet on the forks I put it about 18" off the ground and stepped up and stood on the very end of the forks, 36" out from the fulcrum point. I wanted to see if my 200 lbs out at that distance would make the rear tires lift off the ground.

To my satisfaction, the rear end stayed put quite nicely.

The forks, however, did not. They began bleeding downward within just a few seconds.

There are no leaks that I know of, so I guess it has to be the new spool valve? It's from Northern Tool and claims to have load holding check valves. I thought it would be ok quality, but perhaps not.

Is there anything I should look at in there other than finding that check valve and lapping its seat?

Bob

[Eugen]

Are you sure it's not internal cylinder leak?

[thebuildist]

Are you sure it's not internal cylinder leak?

I hadn't thought of that. I guess I'm assuming brand new cylinders wouldn't have an internal leak. But I guess it's possible. I'm not sure how I'd diagnose that.

Bob

[DavidBarkey]

Are you sure it's not internal cylinder leak?

I hadn't thought of that. I guess I'm assuming brand new cylinders wouldn't have an internal leak. But I guess it's possible. I'm not sure how I'd diagnose that.

Bob

The only way I know of is to raise the the bucket , support it and then remove the line cap fitting creating a external hydro lock, remove support and apply a load . measure and leave for period of time , remeasure and see if it has move any measurable amount . If it has , note new measurement and leave for same amount of time and see if it continues or is just air from opening lines .

[Eugen]

I hadn't thought of that. I guess I'm assuming brand new cylinders wouldn't have an internal leak. But I guess it's possible. I'm not sure how I'd diagnose that.

Bob

If you can assume that the new spool valve can leak, the same applies to the cylinders. For me the big surprise is that it happens on relatively small weight.

I would suspect the relief valve you built first, although I don't remember where it is located in the hydraulic circuit.

[Jancoe]

Ok for testing. Retract the cylinder all the way. Now remove the extend hose at cyl fitting. If you have fluid coming out of the cyl port the cyl is bypassing. If you have it coming out of the hose you are seeing a valve bypass. Next try the cyl fully extended and remove the retract hose and test again.

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[Eugen]

@Jancoe sorry, I'm not really following why fluid would come out of the cylinder. If there is internal bypass, wouldn't the fluid just pass the rod seal from one side of the cylinder to the other, in effect the volume of liquid in the cylinder remaining the same?

[Jancoe]

Ok sorry I didn't finish. When you retract the cyl fully, remove extend hose at cyl. With extended hose removed now activate valve in retract. If fluid comes out of cyl port, cyl is bypassing. If coming from hose the valve is bypassing. Then check with cyl extended and test with valve in extend. This is a very easy way to test cyl and valve issue at same time. You will always get a residual fluid coming from valve due to pressure changes within the valve. You will know if there is a leak when this is performed.

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[thebuildist]

Ok sorry I didn't finish. When you retract the cyl fully, remove extend hose at cyl. With extended hose removed now activate valve in retract. If fluid comes out of cyl port, cyl is bypassing. If coming from hose the valve is bypassing. Then check with cyl extended and test with valve in extend. This is a very easy way to test cyl and valve issue at same time. You will always get a residual fluid coming from valve due to pressure changes within the valve. You will know if there is a leak when this is performed.

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,
I think I follow you. But not running when you test, right?

Bob

[Jancoe]

Yes you will run the engine. Do not run the valve accidentally the wrong direction or you will shoot a high psi stream of fluid out. Cyl retracted. Valve in retract. Your extend side is not pressurized when the cyl is fully retracted. So when hose is off any noticeable small psi stream runs out of either end of cyl or hose you know where it's coming from. Stick the hose in a pop bottle and tape it on. Another bottle to cyl fitting.

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