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Posted for <5zq@cox.net>:
Hello James,
My guess is that you have a somewhat larger problem than bleeding the system.
After retraction, your gear should remain firmly in the well with the doors
tightly shut for a week or so (aircraft on jacks, of course). An external
leak (fluid departing the system), will be quite obvious from a cursory look
at the plumbing. What you've probably got is an internal leak. I had a similar
situation a few years ago. There was a scratch on one of my cylinder inside
walls that would allow pressure to leak from the up side to the down side
inside the cylinder. The scratch was at the down side so I got the repetitive
"burps" of the pump only when the gear was down. When retracted, everything
worked fine.
Here's how to find the leak. I get a supply of plugs and caps (available from
Spruce). Disconnect the lines from one cylinder and cap them. Then test the
system. If you still have the "burps" disconnect another cylinder and cap the
lines. Keep taking one cylinder at a time out of the system until the burps
stop.
Once you've isolated the bad cylinder, you can open it up, inspect it and
rebuild with new o-rings. A torn or worn o-ring could be the problem in which
case your total cost will be a few cents for the o-rings and a few bucks for a
new shirt and a big pile of shop towels. (This is a fairly messy, but not
difficult task). If you find a scratch or other defect in the cylinder tube,
then you'll need to replace the cylinder. This is a bit more expensive, but
nothing that would break the bank.
If you get all of the cylinders out of the system and the burping still
occurs, the problem is in the freefall valve or possibly the pump itself. My
guess, however, would be that you'll find the problem in a cylinder.
Good luck and let us know what you find.
Bill Harrelson
N5ZQ 320
N6ZQ IV
"""
It seems I'm having difficulty bleeding air from my hydraulic system. I
replaced a leaking hydraulic line in the right wheel well. I completed
the job and re-serviced the system. In operation now, the pump burps
for a second every three or four seconds after retraction. This happens
until I pull the relay circuit breaker. When I pull the relay circuit
breaker, the gear partially falls down after a minute or so. The pump
burps continuously after the gear is extended. I've re-serviced several
times, while continuing to run the system after each reservicing in an
attempt to get the air out, with no improvement. I read in the Lancair
Network News (Dec '94, Jan '95 issue #12) that bleeding air from both
sides of the cylinder can be useful, but the article gives no
information on how to actually accomplish the "bleeding" proceedure. """
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