Hydraulics not holding

04zrx said:

that seems weird to me, internal "blow by" is "normal". That just doesn't seem right.

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The spool has to slide easily in the valve body in order to operate correctly. Zero clearance to eliminate the internal leakage means that it won't slide.

Since any clearance will pass fluid under pressure, some internal leakage is normal. Wear from many cycles will increase that clearance, even though it is well lubricated.

Tudor's correct it's completely normal.

When I park my 312 and forget to lower the deck it does the same thing and if it's quiet enough you can hear it creak and pop as it leaks down. Our Deere 544E loader is the same way if you leave the bucket raised and shut the machine off you can hear it pop and creak as the system slowly leaks down.

It's a L&G tractor, not a $80,000 backhoe. There are compromises in components, and always present "how good is good enough" and does the part do the job.

Be glad, you could WATCH the decks drop on the 4x5 tractors right after shutdown.


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All hydraulics have a settle rate. Cat had a spec that was allowed on there dozers that I remember checking. You didn't want the back ripper settling all the way down while you were pushing with the front blade during a push and the oposite-you didn't want the blade going down while ripping.

So take a measurement of rate. How many minutes does it take for one inch. If you are doing 5 seconds an inch or something like that-you need to fix something. Also-locking the cylinder totally out may or may not tell you if it is internally bypassing. Here is why-the rod side has a different volume then the piston side with fluid on both sides. There is no physical way it can bypass through if both sides have been locked out. Different story if only the piston side has fluid.

This is why it is critical to have clean fluid in hydraulics. The dirt will score the valves/cylinders and cause it to loose pressure faster. My hydraulics I likely could leave up for day as I haven't noticed any settling (not that I do leave them up-but it isn't noticed on the settling either). Things do wear out so if it is bad enough tearing into the valve may not be a bad thing. Hours and age isn't as bad as wrong or dirty fluid.