Bleeding Hydraulic Systems

[MV Wanderlust]

Good Morning,

I need to replace our Simrad RPU160 auto pilot pump.

The good folks at Robertson were excellent at walking me through the diagnostics to confirm the motor on the pump was, indeed, bad.

I have the pump. Two wires and three hydraulic fittings. Not difficult to change and I don't mind doing that myself. However, when transferring the hydraulic lines from one pump to the other, fluid is going to leak out and air will seep into the lines. They'll need to be burped or bled afterward. I'm good with electronics and basic mechanical but have never done any hydraulic work.

This pump is in the engine room (under the salon on our aft cabin). The fluid reservoir is under the bed in the master stateroom, aft. The only steering is on the fly bridge (no pilothouse/lower helm station).

Is bleeding the system something that would be pretty easy to do myself or is it something best left to a professional hydraulic mechanic since it involves steering? If it's something that is really pretty easy, could someone please take a couple of minutes to break down the steps for me? Where is the best place to crack open the lines to bleed them... the helm station since it's the highest point and air rises? I admit to not even knowing which questions to ask.

Thanks for any advice.

John

[fabricator-ken]

I changed my hydraulic pump while en route. Did not cause any issues. I just kept the reservoir topped up.
However I have hydraulic steering on the ram there is a bleed nipple similar to bleeding your car brakes. It's a matter of cracking the nipple and turning the,steering in one direction constantly until the bubbles stop. Then turn the opposite and repeat. Ensure the reservoir is continually topped up. Needs two people, not difficult.

[s/v Moondancer]

In my system the auto-pilot pump is mounted 2 ft above the ram and has to be bled independently even though the reservoir is above both.

[Pete7]

John, its not difficult to work through. However, you may need a couple of goes at it, especially if you get a knock when steering which means there is air still in a line or the ram etc. Actually we used to take the rib to sea and bounce it around for a while to work bubbles up to the helm unit and then top up and bleed again.

However, if you have not worked with Hyd oil be aware it goes everywhere Buy a box of nappies and place under anything you intend to undo. Cleaning up GRP afterwards is a pain. Also gloves, paper towels and a small funnel to top up the system. Finally I always seemed to use more than intended so have a spare bottle of oil handy, you can always keep it on the boat.

[fabricator-ken]

John , that is not a problem. Disconnect the pump power wires . Then rig wires so you can power the pump direct from a12 volt source, assuming it's 12 volt. Apply power and Crack the nipple on your ram looking for the bubbles to stop. Top up fluid and reverse the procedure. That is change the wires over to reverse the pump. What your Pilot brain does automatically. You may need to do it a couple of times. Always carry a,supply of oil and general spares as there are no shops when you need them. All the best.

[DeepFrz]

If the oil in the system has been there for a number of years I would suggest you replace all of the oil.

[MV Wanderlust]

Good advice from everyone. Thanks. Think I'll give it a try, myself. Doesn't sound like there is a need to hire someone for this.

[MV Wanderlust]

SUCCESS!
Changed the pump on Saturday. The reservoir was never allowed to drop below the minimum fluid level line. I loosened each line on the old pump, one at a time, and quickly transferred it to the same fitting on the new pump. Based on the amount of fluid absorbed by the oil diaper, the system appeared to lose only about four fluid ounces of oil, total. I topped up the reservoir afterward. The replacement pump works great and the autopilot is back in business. The steering was 6 and 1/3 turns, lock to lock, before starting and after finishing.


Changing the pump was actually pretty easy. The hardest part of the whole thing was crawling behind the starboard engine, over the propeller shaft, under the exhaust pipe and stretching far enough to reach the autopilot motor on a ledge next to the muffler. That was a pain.


Thanks for the tips!