Loader leak down.

[boggen]

*waves a white flag* it finally clicked in me mind.



when i started to draw, and just about to open excel sheet to rough calc volume... for total hyd oil volume in A and B diagrams.
B = more hyd oil in the cylinder vs A diagram, that has less total volume of hyd oil in it.

thanks for keeping at me. was in the old fart mood, stuck in me ways and not about to budge.

 

[LD1]

Glad you got it. I had explained about as best I could, and was ready to throw in the towel.:laughing:

 

[boggen]

what makes for a better spool valve? or any hyd valve used on tractors today's age?

 

[LD1]

what makes for a better spool valve? or any hyd valve used on tractors today's age?

Tighter tolerances.

Remember, as JJ or someone else described, there are no seals in the valve. The spool and body only seal by the extremely exact fit of the spool. The seal is never perfect though. So a very tiny amount of hydraulic oil CAN and DOES leak past the valve. That causes drift.

Obviously, with no seals in the valve, the more pressure you have the faster it will leak. Thus hanging weight on the loader causes faster bleed down.

 

[arrow]

Glad you got it. I had explained about as best I could, and was ready to throw in the towel.:laughing:

LD is seldom wrong. He's got a good head for math and is conceptual, watch: LD, what percent increase is 74 over 70?

 

[boggen]

if hyd oil as it warms up, the viscosity changes, (from syrup to water). why would you want to have hyd oil constantly pumping through the system, warming itself up. vs a cooler / colder hyd oil. that is less likely to leak through and around the spool valve?

is there a better valve, that increases overall length and reduced diameter of spool valve within reason to help reduce leakage within the valve?

if metal to metal sealing, are there check valves inside the unit, that help reduce the leakage through the spool valve?

 

[dfkrug]

Obviously, with no seals in the valve, the more pressure you have the faster it will leak. Thus hanging weight on the
loader causes faster bleed down.

Yes. This animal has been beaten on TBN numerous times, but it is an important concept that bears repeating.

It is important to emphasize that loader boom (or hoe boom) bleed-down is the result of unwanted cylinder
retraction. If you get unwanted cylinder EXTENSION, as BRAIN55 points out above, then forces are trying
to PULL the rod out of the cylinder. Since the valve is closed, the rod-side fluid has nowhere to go. If the
piston seals are damaged (or missing), this force imposes a vacuum on the cylinder, resulting in air getting
sucked into the gland seal. Or cavitation of the oil (less likely). So the bucket or boxblade bleeds down
without any visible oil leaks, and you need to do more investigating before you can blame the
valve or piston seals, or both.

 

[J_J]

With all due respect to your ideas, thoughts and discussions, you all know the loader, BH, just about anything working with hyd, can and does leak

You want a perfect seal, then keep on dreaming.

You also know there are several factors causing it, and for some to say it can't happen is not totally true.

Whether the leak down is caused by the valve spools, cyl piston seals, temperature variation, vacuum leak bent shaft, bore out of round.. It could be one or several conditions that will cause leak down to happen.

In order to troubleshoot and perhaps save some money by purchasing the right part the first time, just might be to your liken.

It does seem like replacing seals fix most leakdown problems. It is the less expensive route.

If a valve spool does leak beyond your expectations, then you have to make a decision whether you want/need a new valve in order to keep your operating standards up.

However if the bad valve is costing you time and effort, then you have a choice.

Purchase new valve and install it your self or take it to a dealer and let them do it for a lot more money.

If you want factory, then buy factory.

You can probably do better using third party venders, and some logical shopping.

So, if you do not want leak down or poor performance, then fix it the best you can.

If you think it is spools, you can use needle valves to shut off all flow through the valve.

What to do about cyl.

To get the lowest leak down on those cyl, you are going to have to educate yourself on seals.

There are many types of seals, and if you choose correctly your leak free cyl might come to fruition.

There is no magic bullet here.

 

[LD1]

LD is seldom wrong. He's got a good head for math and is conceptual, watch: LD, what percent increase is 74 over 70?

5.7%

And 70 is 5.4% less than 74

 

[arrow]

5.7%

And 70 is 5.4% less than 74

74-70=4…… 4/70=.057x100=5.71%…..told ya.

Does anyone have a tractor that doesn't leak down a bit? It takes about 4 days for my fel to go down a foot. The 3 pt doesn't seem to move.