Bleeding Hydraulic Ram on Autopilot

[svcattales]

I just replaced the rubber pressure lines from hydraulic pump to the push-pull ram of my autopilot. I have a small hydraulic oil reserve on top of the pump and it looks like bleed nipples on both ends of the ram. What is the correct technique for bleeding the air out of the new lines and the ram? The hydraulic pump is spun by a small reversible DC motor.

[Blue Stocking]

If this is the stand-alone pump and ram actuator type, elevate the pump so that the lines continuously rise, and cycle the piston, That should expel the air. It may take some time.

[speciald@ocens.]

Turnn the wheel from lock to lock repeatedly and the air should pass to the reservoir.

[svcattales]

Originally Posted by speciald@ocens.

Turnn the wheel from lock to lock repeatedly and the air should pass to the reservoir.

Thanks. I forgot to mention that the pump is about 2 ft below the hydraulic ram so I believe I need to pressurize the system with pump. There is really no room to unbolt the pump/motor assembly and raise it higher than the ram.

[Blue Stocking]

If this is the assembly that consists of a pump connected to the ram directly, by two hoses, and the pump is lower than the ram, then turning the wheel is not likely to displace the trapped air.
In this case, you will probably have to bleed the air out by way of the fitting attached to the ram. They should be a T fitting with a needle valve as part of the fitting. Connect clear plastic tubing to each valve, and lead them upwards into a container of fluid, With the ends always submerged in the fluid, and the escape valves open, you can slowly work the ram back and forth and watch the trapped air rise, and be evacuated. By moving the ram piston back and forth, you pressurize the air out of one line, while vacumning no-aerated fluid in thru the other. It is generally a time comsuming process.
With the ram ball-joint diconnected from the steering head, you don't need to power the motor to purge the system.
I have carried out this procedure many times as a ComNav installer.

[Mark Zarley]

If it is a 2 pump system . The motor pump assembly is the auto pilot. The pump driven by armstrong and connected to the big round steering wheel is the one to use, Lock to lock is the ticket.

[svcattales]

[QUOTE=Blue Stocking;543974]If this is the assembly that consists of a pump connected to the ram directly, by two hoses, and the pump is lower than the ram, then turning the wheel is not likely to displace the trapped air.
In this case, you will probably have to bleed the air out by way of the fitting attached to the ram. They should be a T fitting with a needle valve as part of the fitting. Connect clear plastic tubing to each valve, and lead them upwards into a container of fluid, With the ends always submerged in the fluid, and the escape valves open, you can slowly work the ram back and forth and watch the trapped air rise, and be evacuated. By moving the ram piston back and forth, you pressurize the air out of one line, while vacumning no-aerated fluid in thru the other. It is generally a time comsuming process.
With the ram ball-joint diconnected from the steering head, you don't need to power the motor to purge the system. [QUOTE]

Thanks Blue Stocking. You described my setup and your solution makes good sense. I don't have a tee fitting on the ram, but there are nipples on both ends of the ram which I think will work the same way. If I hook up the plastic hoses as you suggest, the ram should suck fluid up to one side and then the other while expelling air out the top. I'll have to refill the reservoir often as fluid gets sucked up into the lines. I'm wondering if I can do this same process by operating the pump by just hooking up the motor leads to 12V DC and changing polarity to reverse the direction? I'm not sure how hard it will be to move the ram manually, but I'll give it a try.

[Blue Stocking]

The set-up you have is referred to as a linear actuator, and has the advantage of giving you a second steering source, by way of the a/pilot, should your main steering fail. On a sailboat, I would not recommend any other way.
The ideal purging system would be by having the seperate fluid reservior higher than the ram, That way, all air can rise, and the fluid can transfer without inducting air.
Another method would be to modify the pump reservoir cap with a pipe fitting, and hosing it, with a seperate container, up to a point higher than the ram, and putting the purge fluid at the highest point above the ram.
The bottom line is, in this type of closed system, any air MUST rise to a bleed point to escape.

* Go to Comnav website and see their ideas on this this.
I have no connection with them, but have installed their a/pilots in the past.

[r.furborough]

If the pump is a reversing type it would probably be best to disconnect the pump from the course computer (make a note of the connections) and connect it directly to a 12V DC source, this way you can run and reverse the pump at will while controlling the bleed from the cylinder. This will evacuate the air from the pump, you will still have to manually bleed the air from the helm though. BIf you did not note the connection when disconnecting the pump from the computer and you get the connections reversed, you will not damage anything and the computer will try and turn the boat in the opposite direction. Just reverse the connection and you will be done.

[S/V_Surya]

I don't know what kind of autopilot you have or ram but I am installing a new system on my boat. A comnav 1420. If you go to web site and download the manual it has a section on bleeding the ram unit. I would like to ad that I am not geting much help from any of the local dealers on getting assitance on setting mine up. My old system had hydraulic reservoir on top of pump. New pump needs external reservoir. If anybody has been down this road let me know.

By the way I am getting rid of the old pump if any one is interested. Need new motor but solenid and externals seem fine. Looking at the expense of these pumps someone may be interested. Also the old autopilot was navico which is going in the trash unless somebody wants it.

[Blue Stocking]

1420 is a nice set-up Moving the reservoir off the pump solves, for some, the very problem OP has.

[svcattales]

Originally Posted by Blue Stocking

The set-up you have is referred to as a linear actuator, and has the advantage of giving you a second steering source, by way of the a/pilot, should your main steering fail. On a sailboat, I would not recommend any other way.
The ideal purging system would be by having the seperate fluid reservior higher than the ram, That way, all air can rise, and the fluid can transfer without inducting air.
Another method would be to modify the pump reservoir cap with a pipe fitting, and hosing it, with a seperate container, up to a point higher than the ram, and putting the purge fluid at the highest point above the ram.
The bottom line is, in this type of closed system, any air MUST rise to a bleed point to escape.

* Go to Comnav website and see their ideas on this this.
I have no connection with them, but have installed their a/pilots in the past.

Blue Stocking, I used your manual bleeding method today and it worked great. The ram was easy to pull in and out by hand and I could see the air escaping through the bleed tubes. Getting the oil container above the ram was the real trick. I had to make a little shelf out of plywood to set on top of the steering quadrant and put the quart of hydraulic fluid inside a coffee can to keep it from tipping and falling on my head. After bleeding I turned on the autopilot and cycled the ram back & forth several times. Everything worked fine.

Thanks again for the great advise.

[Blue Stocking]

Originally Posted by svcattales

Blue Stocking, I used your manual bleeding method today and it worked great. The ram was easy to pull in and out by hand and I could see the air escaping through the bleed tubes. Getting the oil container above the ram was the real trick. I had to make a little shelf out of plywood to set on top of the steering quadrant and put the quart of hydraulic fluid inside a coffee can to keep it from tipping and falling on my head. After bleeding I turned on the autopilot and cycled the ram back & forth several times. Everything worked fine.

Thanks again for the great advise.

Go sailing--you have earned it.

[morgan38]

I have a Octopus linear drive and pump. On a recent cruise to the Bahamas, the drive worked well for the first 200 miles, leaking little if any fluid. Then it started to get air into the hydraulics. I would bleed it, and it would work well for 30 minutes maybe an hour even when lightly loaded. I prefer repairing things myself, but Octopus wants me to send it in or buy a new system (default statement?).

Is this air leak likely due to warn seals in the cylinder, pump or somewhere else? Is there a way to isolate the problem to pump or cylinder?

The Octopus procedure for rebuilding the cylinder does not appear to be difficult. Their rebuild kit includes seals and o-ring for all their models. I would expect the seals for the cylinder are metric hydraulic parts such as U cup seals. So I would prefer to get just what I need locally. Has anyone else tried this?

Any feedback is appreciated.

[svcattales]

Originally Posted by morgan38

I have a Octopus linear drive and pump. On a recent cruise to the Bahamas, the drive worked well for the first 200 miles, leaking little if any fluid. Then it started to get air into the hydraulics. I would bleed it, and it would work well for 30 minutes maybe an hour even when lightly loaded. I prefer repairing things myself, but Octopus wants me to send it in or buy a new system (default statement?).

Is this air leak likely due to warn seals in the cylinder, pump or somewhere else? Is there a way to isolate the problem to pump or cylinder?

The Octopus procedure for rebuilding the cylinder does not appear to be difficult. Their rebuild kit includes seals and o-ring for all their models. I would expect the seals for the cylinder are metric hydraulic parts such as U cup seals. So I would prefer to get just what I need locally. Has anyone else tried this?

Any feedback is appreciated.

Morgan, It's worth a try to try and find the replacement parts from a local source. There could be some commonality with auto brake seals, but finding the right ones may involve looking at a bunch of different seals to match them by dimensions. If you find a really good auto-parts expert, he/she may recognize the seal type and help you search.

Trouble shooting the air source: Perhaps you can cycle the pump on and off to see if bubbles show up in the reservoir while you watch it. If you see bubbles, I would suspect the pump seals. It would be nice to have transparent lines for testing, but don't know if any clear hoses could handle the pressure. With clear lines, you might see where the bubbles originate.
Good luck,