Air in Autopilot System

[LPL]

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 visible.

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.

Thanks,
Paul

[DeepFrz]

Are you using a tube from the bleed fitting to a jar with hydraulic fluid in it so that the tube end is always submerged in fluid? If the tube is not submerged you may be sucking air back in through the bleed fitting. Otherwise, very carefully check your hoses, end to end, and all fittings to make sure everything is tight and there are no leaks. I wonder if you could be getting air in at the pump.

Did you ever run low on fluid or did you have to keep refilling with fluid before you started working on the system?

[s/v Jedi]

If your system is like mine, yo have a Hynautics reservoir (reservalve). You can pressurize it with the car-tire valve on top of the housing. After I pressurized it, bleeding was finished in minutes. I used the instructions on the reservoir.

cheers,
Nick.

[LPL]

DeepFrz

Yes, I have clear tubing on both bleed tees which run to a container with oil, and they are kept submerged. I have checked all the tubing and fittings.

I also thought the pump would be a possibility, but have no idea where it could be getting air from.

[LPL]

S/V Jedi

I just have reservoir with a screw on lid--no presure. But I am going to look into installing one like yours.

[s/v Jedi]

Originally Posted by LPL

S/V Jedi

I just have reservoir with a screw on lid--no presure. But I am going to look into installing one like yours.

I really think all WH pilots come with the hynautics reservalve.... Is it possible somebody replaced it for your current one?

I bleed 99% of air at the cylinder fittings. A pressurized reservoir makes this almost a fun job.

cheers,
Nick.

[LPL]

Jedi

WH shipped the system to me, then I shipped it to the installer and it came with a regular jar (no fittings except where it leads to the pump) with a screw on lid. Will confirmed this, but I didn't get an explanation why. I wish I had one like yours, because I could really use some fun right now.

Thanks for your replies, I may pursue that route and save my motor.

[r.furborough]

I think your bleeding process is wrong - Try removing the hydraulic pumps 12 volt supply wires from the autopilot unit (note the polarity for reconnection) and use the autopilot 12v supply to power the pump to bleed the system, reversing the wires will reverse the pump to reverse the fluid flow during the bleeding process.

[s/v Jedi]

Originally Posted by LPL

Jedi

WH shipped the system to me, then I shipped it to the installer and it came with a regular jar (no fittings except where it leads to the pump) with a screw on lid. Will confirmed this, but I didn't get an explanation why. I wish I had one like yours, because I could really use some fun right now.

Thanks for your replies, I may pursue that route and save my motor.

This means he switched reservoir brand. I think Hynautics was acquired by Teleflex or something? But the Hynautics reservalves are still available.

cheers,
Nick.

[LPL]

Nick

I think I will bite the bullet and get the Reservalve. Ouch!! I hope there is gold inside.

When you say you bleed 99% at the cylinder fittings---where do you bleed the other 1% from? Or do you just let it find it's way back to the reservoir?

One thing I worry about, is the installer has the bleed tees on the side of the cylinder instead of on top. But he got it bled and it worked fine for 2 1/2 years. I would have to buy new hoses an inch or so longer and buy yet another set of bleed tees to change things to the top.

Thanks for your help.

f.furborough

I might be missing something, but the WH system will run the dogde buttons (Red/Green 10 degrees or more if held down) in the standby mode thus enabling the hydraulic pump to push fluid to either end of the ram. That seems to do the same thing you are talking about.

Thanks,
Paul

[s/v Jedi]

Hi Paul,

I did the bleeding in 2 phases. First turning the rudder from end to end, bleeding at the cylinder fittings every time (push the rudder hard). After all that, I used the auto-pilot and think I opened the manual by-pass valve so that the hydraulic motors keep running. Air bubbles that arrive at the reservalve are trapped in there (they bubble up to the top of the reservoir).

I must have some photo's of the labels on the reservalve that describe the procedure but didn't find them yet... must have been made before I started uploading everything to SmugMug. I'll try to find it.

My cylinder has the fittings on the side too and it wasn't a problem.

What I don't understand is why the bleeding procedure worked 2.5 years ago with your current reservoir? Does it have the bleeding valves underneath at the hose connections? I'm not very good at hydraulics so can't help much more...

ciao!
Nick.

[r.furborough]

Paul,

It depends if the pump runs sufficiently to purge the air from the A/P lines and through the helm line to the ram. Another point is that normally it would take two people to do this as the valves need to be closed before the pressure drops in the system and air is drawn back in. Only other was is to pressureize the system or find a company that will loan or hire you a Teleflex power purge system with the correct fittings.

Bob.

Originally Posted by LPL

Nick

Thanks for your help.

f.furborough

I might be missing something, but the WH system will run the dogde buttons (Red/Green 10 degrees or more if held down) in the standby mode thus enabling the hydraulic pump to push fluid to either end of the ram. That seems to do the same thing you are talking about.

Thanks,
Paul

[DeepFrz]

Bob,
Air wont be drawn back into the lines so long as the bleed line is kept immersed in fluid.

I guess the thing that I neglected was to ask about the configuration. Is it strictly AP or is the helm also hydraulic. If strictly AP then the method you are using should work.

One other thought is that you aren't pumping out enough fluid to get rid of all the air in the bleed line so that air keeps getting drawn back into the system. Then it would be necessary to keep the system pressurized until the bleed fitting is closed. You could rig up a reservoir with a fitting in the bottom for the bleed line and keep the bleed line angling up at all times. That should allow all the air to rise up into the bleed reservoir.
Good luck.

[LPL]

Nick, DeepFrz and Bob,

Thanks for all your replies. I think we (my wife and I) finally succeeded. I took enough stuff apart and put them back together that I'm not positive what the culprit was, but I think we got it. I was going to order a reservalve this pm, so was glad to save some bucks. I'm leaving everything hooked up overnight (with the tees closed) so that I can hit it a couple of times tomorrow to make sure all the air is out. I appreciate all your replies. Wish me luck tomorrow.

Thanks,

Paul

[s/v Jedi]

You know, with stuff like this there are 2 possible approaches:

1. never touch it and just hope it keeps working (many do that with engine too, for example)

2. get to know the gear in detail; study it, disassemble it, clean it, put back together, bleed, tune and shine it. This takes more of your time but it also means this gear is never gonna bite you on passage.

#2 is how professional organisations maintain their gear. I use #2 too because I'm too curious and want to know how everything works. Your hydraulics pack is now getting #2 attention from you too

ciao!
Nick.