Cylinder Leak Down test?

[LD1]

Im thinking the oil is seeping past the seals so the oil is displaced to the other end of the cylinder. Much like if an engine has bad ring seals the combustion mix can enter the lower end. Sorry Im still at a loss. And more confusing where some people are talking the valve. The valve is completely disconnected so the issue must be with the cylinder rod seals.

You are thinking about it all wrong.

The oil simply cannot bypass the piston. Because the rod side is already full of oil.

Your engine analogy is not assuming a sealed and closed system. PCV valve can vent back to intake. And besides....gasses are compressible, hydraulic oil is not.

Imagine this, take a glass and fill it clear to the brim with water.nthisbrepresents your cylinder.

Now take a broom handle and stick in the glass. What happens to the water? It overflows right? And the further you push the broom handle into the glass, the more water spills out.

Same concept with your loader. In order for the cylinders to compress.....the volume of the cylinder rod entering into the cylinder displaces oil. That oil has to leave the system somehow. And the only way is either back through the valve, or a leak onto the ground.

That's why you are being told it's a valve issue.

The fact that you are saying it still does it even with the valve disconnected warrants further investigation. Because with the valve disconnected.....the ONLY way you can compress that cylinder is either 1. Oil is leaving the cylinder or 2. The cylinder isn't full of oil to begin with.

1. Could be a leak you aren't seeing OR you disconnected the wrong couplers

2. Could be air in the system. Low on oil sucking air, or a leak in the suction hose to the pump could cause this.

Not saying your cylinders aren't wore out and in need of rebuilding....but that's a whole other test with different symptoms. With loader drift....you are barking up the wrong tree thinking cylinder seals. Since you like engine analogies.....that would be like thinking replacing your water pump is gonna fix a low oil pressure situation...

 

[Tx Jim]

Now take a broom handle and stick in the glass. What happens to the water? It overflows right? And the further you push the broom handle into the glass, the more water spills out.

Same concept with your loader. In order for the cylinders to compress.....the volume of the cylinder rod entering into the cylinder displaces oil. That oil has to leave the system somehow. And the only way is either back through the valve, or a leak onto the ground.

That's why you are being told it's a valve issue.

I like your example of full glass of water with broom handle inserted which causes overflow or water. Very simple to understand & very difficult to dispute!!!

 

[Bedlam]

Piston can bypass internally...

Wouldn't the oil 'go' to the other end of the cylinder? there was no leaking on the floor.

You are thinking about it all wrong.

The oil simply cannot bypass the piston. Because the rod side is already full of oil.

Your engine analogy is not assuming a sealed and closed system. PCV valve can vent back to intake. And besides....gasses are compressible, hydraulic oil is not.

Imagine this, take a glass and fill it clear to the brim with water.nthisbrepresents your cylinder.

Now take a broom handle and stick in the glass. What happens to the water? It overflows right? And the further you push the broom handle into the glass, the more water spills out.

Same concept with your loader. In order for the cylinders to compress.....the volume of the cylinder rod entering into the cylinder displaces oil. That oil has to leave the system somehow. And the only way is either back through the valve, or a leak onto the ground.

That's why you are being told it's a valve issue.

The fact that you are saying it still does it even with the valve disconnected warrants further investigation. Because with the valve disconnected.....the ONLY way you can compress that cylinder is either 1. Oil is leaving the cylinder or 2. The cylinder isn't full of oil to begin with.

1. Could be a leak you aren't seeing OR you disconnected the wrong couplers

2. Could be air in the system. Low on oil sucking air, or a leak in the suction hose to the pump could cause this.

Not saying your cylinders aren't wore out and in need of rebuilding....but that's a whole other test with different symptoms. With loader drift....you are barking up the wrong tree thinking cylinder seals. Since you like engine analogies.....that would be like thinking replacing your water pump is gonna fix a low oil pressure situation...

AHH I see what you mean now. I hadn't thought of the 'exposed' rod entering and having to displace the oil..Because the rod takes up space inside the cylinder. Not sure why I hadnt thought of that. Makes a difference..

But yes after running it for awhile. I raised it up half way and supported it on the transmission jack. then lowered the weight to have it rest on the jack. I then disconnected the correct two quick disconnects. Then lowered the Transmission jack and measured the height it was at. (forks on) then I took note of the time and went and did other work until an hour was gone by. I remeasured it and there was a 2 inch difference from the hour previous. And no leaks anywhere. I keep it well clean (but not waxed) lol and it was on a concrete floor. Maybe it wont increase then dropping in the future. unless something changes I will recheck it in the fall.
But I hadn't thought of the displacement of the cylinder as it enters. Good catch.

OH BTW if I leave it 3/4 up a few days later its fully down. (of cource that's with the connects hooked up. (normal operation)

 

[LD1]

2" over an hour is nothing. And probably just a little air working out.after your 1hr measurement...go back an hour or two later and I bet it hasn't moved.

3/4 to full down over a few days with the valve in the circuit is probably valve leakage. And even that might not be considered excessive. The spools are metal on metal seal and very tight tolerances. But no actual seal....so some leakage is expected and normal.

Glad you are gaining an understanding of how it works now