Power bleeding a steering system

[Charlie]

Hi All:

I have a an autopilot that is difficult to bleed. Recently I bled the clutch in a 1976 BMW and the consensus was to push the fluid thru the clutch as opposed to using the bleed screw. I would like to try this on my AP. Problem is that I used a 1 pint hand pump to bleed the clutch and that is too small for the AP. Can anyone recommend a pump that would push hydraulic oil thru the system? would this work?

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[delmarrey]

Hi Charlie,

Assuming you have bleed screws on the cylinder that can hold hoses, why not just run the AP port/stbd while keeping oil in the reservoir.

Otherwise would a brake fluid bleeding system work? They may be rentable.

[Charlie]

Del I have spent hours trying to get the system bled to no avail. There are a lot of hills and valleys in the system. On top of that the eletric motor that runs the hydraulic system seems to hold air as well. My idea i to push all of the oil through the system in order to ensure there is no air. The one time I got it to work reasonably well I had to disconnect everything and pull the pump out of the boat and straighten out all the hoses. It was a PITA. Trying to figure out a different way nw.

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[delmarrey]

Hi Charlie,
Hills, valleys and loops shouldn't make any difference. It sounds like the pump is sucking air. Once the system is pressureized it should push all the air out the very end (cylinder). Air compresses, liquid does not. Even if the lines were totally empty you should be able to force all the air out the last fitting.

I think I would pull the pump off the reservoir and check the suction tube, or the source of the intake, which ever it may be. It's much like a fuel system on the diesel motors. All the fittings need to be tight, even at the pump. Once the pump is primed and has a source of product it should continue pumping until the product runs out, thus causing more air in the system.

Another method is to pump from the lowest point up, like on an outboard/outdrive.

[Charlie]

Hi Del

My idea is to pump from the lowest point and force the fluid up through the system. I am trying to figure out how to do that. When I bled the clutch I used one of those little oil squirt pumps. I'm not sure I could do that here because of the volume needed to fill the system and because of the strength of the pump.

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[delmarrey]

Like I said earlier, maybe a break fluid bleeder pump system, but don't know for sure. Or look on eBay for a lift pump w/reservior for a above ground car hoist.

Anyway, the problem you may run into are check valves. It would probably be wise to go from both ends of the steering cylinder.

[seabreez]

Originally Posted by Charlie

Del I have spent hours trying to get the system bled to no avail. There are a lot of hills and valleys in the system. On top of that the eletric motor that runs the hydraulic system seems to hold air as well. My idea i to push all of the oil through the system in order to ensure there is no air. The one time I got it to work reasonably well I had to disconnect everything and pull the pump out of the boat and straighten out all the hoses. It was a PITA. Trying to figure out a different way nw.

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I am sure you are using the appropriate oil. Some systems need to disconnect the line to get the volume of oil through the valley and humps to purge the air out. All systems are setup to get rid of the air. What color is the oil? Is it foaming? Indicates the air is not getting out or the wrong oil. Is the pump higher or lower than the reservoir?

[delmarrey]

Originally Posted by seabreez

Is the pump higher or lower than the reservoir?

Anouther good point for an external reservoir!

[Charlie]

Del thnx for the ideas. I will look for a brake bleeding kit. I have a Mittyvac but don't think that will work. Do you think using an oil vaccum pump would work if I put it on the top of the system and had it draw the oil from the bottom?

Seabreez I am not positive about the oil. It was 8 years ago when I installed it. I bought the oil in Mexico but inspected the container it came out of.

The reservoir sits above the pump by 16" or so. As for bubbles I don't remember the oil being aerated.

A hydraulics mechanic said the most likely place for air infiltration was the reservoir. Thoughts?

[delmarrey]

I'm a certified hydraulics mechanic among other certs. If air gets in the system the foam will get returned to the tank and the bubbles gets picked up again causing a vicious circle. One has to let the foam settle before proceeding making sure the tank is full.

Does the pick up from the reservoir come from the top or bottom?
As for whether a vac system would work, I'd have to see it with my own eyes. All you can do is try.

[Charlie]

Will take pics this weeend

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