Hi all. I have a 40 foot sailboat with cable steering
and a WH hydraulic autopilot
system that is attached to the rudder
post. The unit is quite robust and has served us well for 2 1/2 years until, somehow a little air got into the system.
I have spent many days unsuccessfully trying to purge the air from the system. There is a 2/3 quart resovoir of hydrolic oil
mounted 6" above the hydraulic pump (not presurized). The pump and resovoir are higher than the cylinder. The curves in the hoses are of reasonable radius.
I set up the bleeding process with the two bleed tees on either side of the cylinder open, with clear hoses run from the tees to a container with hydraulic oil
in it. My procedure is to manually turn the wheel
from side to side with the bypass handle pulled out. This sucks in solid oil on one side and blows out oil with air bubbles on the other side.
This is followed by closing one bleed tee and pushing the opposite side dodge button. This is with the autopilot
in the standby mode and the tee handle pulled out. After that the tee handle is pushed in and the same dodge button is pushed until no air bubbles are present. Then this procedure is repeated on the opposite side. The only problem is, I am never able to clear the system of air--and trust me, I've blown out enough air to fill a 55 gallon drum.
The resovior is kept filled above the strainer and the bleed hoses are kept submerged in oil. There are no oil leaks
anywhere and yet air is definitely getting into the system. I don't know how air can get in if oil can't get out.
I took the cylinder (BA 150-TM HC5369 by Teleflex) out and had it resealed at a hydraulic shop (regrettably I was not able to watch/police the process). I reinstalled it but still couldn't get rid of the air. Then I ordered new bleed tees still with no success. I thought about isolating the cylinder, hooking it up to bleed tees and hoses and oil, then pushing the ram in and out to see if the air is entering through the ram. Don't now if that will work.
Is there any way that it could enter via the pump--once again, no leaks
I've spent enough time and money
on this already that I would be glad to buy a new cylinder if I knew it would fix my problem. Any ideas???? Any help will be much appreciated.