FEL wont stay up

[J_J]

Just went to put the boom down fully. The boom ends were now about 3ft off the ground. I let the boom down a few inches and returned the valve to neutral.
From this position and with the valve in neutral, the boom continued to the ground by itself without stopping. This was with the engine off. With the engine on, it does not do this with the boom in a lowish position.

Bad valve parts. Worn spool, leaking load check, valve not centering.

 

[Tx Jim]

Some of you are so hard headed, and set in your ways, and stuck in your beliefs that you fail to find/research what is right/correct.

If you don't believe that a cyl will descend with bad seals, then place your head under the bucket and see if your faith is secure.

This excerpt is from Prince and tells how to determine cyl seal leakage.

Place a load in the bucket that induces a pressure reading in the boom cylinder base end of approximately 1000 psi. Raise to approximately mid-stroke. After a short period of time note the pressure on the rod end side of the boom cylinders. It should be near zero and not increasing. If it is not near zero or is increasing, oil is leaking past one or both of the boom cylinder piston seals and the cylinders need to be repaired or replaced.

Prince Hydraulics > Support > Loader Valve FAQ

I could forgive you all for calling me a liar, but I want.

That test you refer i to determine if there is a leaking piston packing BUT has nothing to do with whether FEL boom will settle or not.

I asked you previously if boom cylinder is retracting from boom settling where does the oil go if it can't leak externally as cyl rod continues to use up more area inside cyl bore as cylinder retracts eliminating area needed for the oil??? Do the math. A fully extended 3 X 20 inch cylinder has 141.4286 cubic inch volume then when fully retracted with a 1.5'' in dia rod that takes up 35.3571 cubic inches then where does this 35+ cubic inches of oil go if there's no external leak. That's similar to attempting to put 7#s of flour in a 5# bag or 5 qts of oil in a gallon bottle.

 

[MtnViewRanch]

Brian
For boom to settle lift cylinder piston must move into barrel of cylinder. """""""Where does the extra space come from that cyl rod will occupy that must displace the oil?????""""" If rod seal isn't leaking and control valve is holding a leaking piston seal will not cause FEL boom to settle because there's not sufficient area in cyl bore for trapped oil plus the rod. This principle is the same as a single acting cylinder on a combine platform or Mo-Co lift cyl. as in parts photo only snap ring in single acting cyl acts the same as piston(if packing is leaking) & nut in double acting cyl and just keeps rod from coming out of cyl bore. Piston packing on boom cylinder allows cyl to put down pressure on boom. In parts photo hyd oil pushes cyl rod out of bore but snap ring stops travel when header is lifted.
Thanks,Jim

Jim, you answered the question, there is no place for the oil to go IN THE CYLINDER, the control valve would have to be bad. The OP started out with lifting his front end off the ground with his loader. The front end then proceeded to settle down to the ground. But with this test, he has no absolute starting place. Either the piston seals are bad or the control valve is bad. A rod can be pulled out of the piston if the seals are bad. Plenty of room for the oil to go to on the base side of the cylinder. That is why I said to extend the ram and see if it falls. It can only collapse if the valve is bad. That is why when testing cylinders, you ALWAYS want to extend them for the test, to collapse is impossible on a closed up unit.

Here is a video showing internal leakage, the ram can be pulled out.

 

[Tx Jim]

Brian
Thanks for your reply. In my older age sometimes my reading comprehension leaves some things to be desired.
Thanks again,Jim

 

[LD1]

That is why when testing cylinders, you ALWAYS want to extend them for the test, to collapse is impossible on a closed up unit.

Not according to some. Hence why we have these long debates about every other month. Some just cannot grasp such a simple concept.

Same principal for why crossover valves dont work on DA cylinders.
And same principal that allows SA cylinders with only a packing nut and no piston to operate.

The fact that a SA cylinder (as described above), doesnt just bleed off when the valve is returned to neutral should be proof enough that bad seals wont allow a cylinder to retract. But some are just too bull-headed and continue to give bad advise

 

[MtnViewRanch]

One of the problems when people trouble shoot things is that they do not isolate things. There can only be a single variable at a time to truly determine what the problem is. No different than the OP. He raised his tractor using the loader and has a bleed off problem. But in his problem with how it was determined that he had a problem had 2 variables. That is why I said to raise the loader and see if it still fell. The only variable is the control valve. If it fell, then there was a valve problem, how fast it falls determines if he feels it has to be addressed or not. :confused3:

 

[J_J]

If you want a definitive answer as to whether the piston seals are leaking, do this.

Install needle valves on both lift arms work ports.

Grab a good load of dirt and raise the bucket to max and shut off engine and valve in neutral.

Shut off needle valves.

If the lift arms move any, then the piston seals are leaking.

 

[Tx Jim]

Shut off needle valves.

If the lift arms move any, then the piston seals are leaking.

And just think you called me hard headed. FYI with both needle valves closed that you recommended the boom can't settle because any oil that might leak past piston seals oil is trapped by the needle valves.

 

[J_J]

And just think you called me hard headed. FYI with both needle valves closed that you recommended the boom can't settle because any oil that might leak past piston seals oil is trapped by the needle valves.

What I said was that with the needle valves closed off, there would be no fluid to the spools.

If the lift arms did move, what do you think would cause that to happen. You only have one guess.

With a pressure differential of 1000 psi, is it possible for fluid to transfer from a high pressure side to a lower pressure part of the cyl. Perhaps until the pressure were equal on both sides of the piston.

If the base end of a cyl contains about 50 cc of fluid and the rod end potential volume is about 30 cc, is it possible that 30cc of fluid from the base end might transfer to the rod side, until the pressure on both sided of the piston is equal.

I will say this again. The valve spools is the major cause of loader drop. Did you hear that?

Why have none of you made any definitive statement that worn spools is the only way that a loader can drop?

 

[Tx Jim]

There are no replaceable seals on a spool valve that can leak that will allow a hyd cylinder piston to move. Worn spool lands &/or valve housing can let cylinder piston move.

J_J
Does this statement not qualify about worn valve being at fault for boom settling????
Happy trails,Jim