Loader leak down.

[J_J]

Seems like you have a tight hyd system.

How old is your machine?

How many hours on the machine?

Leakdown occurs differently for each hyd machine, even in the same year.

 

[arrow]

Seems like you have a tight hyd system.

How old is your machine?

How many hours on the machine?

Leakdown occurs differently for each hyd machine, even in the same year.

Oct 2013. Has 43 hrs. My other tractor started moving down almost immediately but that one was 28 years old.

 

[CJONE]

A cylinder will leak down with bad piston packing if the load is held by the cylinder under extension. The rod going out causes a vacuum in the base end but it still does not stop it from creaping. Less fluid in the rod end [because of rod volume] goes into the base of the cyl. I have had cylinders under extreme load [oilfield] blow the gland packing and/or o-rings out because high rod end pressure under compression but it still will leak down. Just been my experience, don't shoot me. When I design power units for industrial application I now use double PO checks because the quality of a standard control valve is so poor you cannot rely on them holding a cylinder in place anymore and most customers are too cheap to buy quality valves like Dynex. So like JJ said valve seals have nothing to do with cylinder holding. And technically for a double P/O check to work correctly the control valve has to be open to tank in the center position. [motor spool] CJ

 

[LD1]

So like JJ said valve seals have nothing to do with cylinder holding. And technically for a double P/O check to work correctly the control valve has to be open to tank in the center position. [motor spool] CJ

It does in our tractors and backhoes. Cause they dont use PO check valves. So if the valve leaks, the cylinder bleeds.

 

[J_J]

You all know the loader arms, BH boom, etc leak down. Some, more so than others. It is just a fact, and really no mystery.

If you really want to know what is leaking, install needle valves and you will know.

If you raise the loader up and close off the needle valve, and the lift arms drop down, you have your answer.

If you can force fluid past the piston seals, with opposite port open, then you also know your answer.

To check the pressure holding ability of the valve, a manual hyd pump with gage will tell you the story.

You can also set the relief valve using the manual hyd pump.

 

[CJONE]

It does in our tractors and backhoes. Cause they dont use PO check valves. So if the valve leaks, the cylinder bleeds.

You need to reread this. It says the valve SEALS have nothing to do with cyl holding. And they don't. I also understand how a tractor hydraulic system functions. I have repaired enough of them after others have messed them up. CJ

 

[CJONE]

You all know the loader arms, BH boom, etc leak down. Some, more so than others. It is just a fact, and really no mystery.

If you really want to know what is leaking, install needle valves and you will know.

If you raise the loader up and close off the needle valve, and the lift arms drop down, you have your answer.

If you can force fluid past the piston seals, with opposite port open, then you also know your answer.

To check the pressure holding ability of the valve, a manual hyd pump with gage will tell you the story.

You can also set the relief valve using the manual hyd pump.

Yep, I always USED to suggest putting a ball valve in at the cyl base. But anymore you have to be careful about liability. Sooner or later somebody will raise the loader and unhook the hose, I just know it!! CJ

 

[J_J]

The needle or ball valve is primarily for testing and working under the front of the machine.

I also use a cyl block to lock cyl.

 

[LD1]

You need to reread this. It says the valve SEALS have nothing to do with cyl holding. And they don't. I also understand how a tractor hydraulic system functions. I have repaired enough of them after others have messed them up. CJ

Technically correct.

But in the context of this thread, I assumed (maybe wrongfully) the valve-to-spool body sealing surfaces is what was being talked about. Even though technically there isnt a seal there.

 

[J_J]

I have seen this tolerance from different manufacturers on the valve spool to bore clearance on hyd valves when new.

Excerpt:

0.0002" diametral clearance is about the "Goldilocks zone" for hydraulic spool valves. Any looser and they leak down, Any tighter and they stick.


Then you have heat and cold, viscosities differences, and also wear and tear.