Autopilot noise at helm

Sounds to me like his whine is intermittent, meaning its not originating from the helm pump or the engine pump, not unless it's constant bypass bleed from the helm pump via the engine pump flow. But he should be able to replicate the whine with the engine off and use of the pilot pump only, in a quiet environment. Using the pilot helm control to make the pilot pump work.

But what I see of his plan he's off to a good preventative start.

Some might say rebuilding the pump is an unnecessary first step. But I agree with your approach. For $180 you get piece of mind and hopefully go thru your system once and be done. Replacing the filter, fluid and bleeding the system will be a bit tedious. I certainly wouldn’t want to do that and then find out you have to rebuild the pump anyway. Then you would have to bleed the system all over again.

While I agree, if failure is happening at the pilot pump, you'll note some issues in the helm pump rebuild. I think it's an overall good preventative first step that narrows the issue down to, eventually, the pilot pump. In fact, as you've noted the tediousness of the overall project, if there is a good, working spare pilot pump on board, I'd swap that during this clean out process. My hunch is that his whine is the pilot pump on its way to the shop. But cleaning everything, refreshing the helm pump, swapping the filter and flushing the lines leaves you in a very good state of mind with regards to the steering. Note to self: drop the rudders on the next haul to check bearings and seals. Well, not to self because I just went through all of this.

Is your pump 12v or 24v? If it is 24v and you decide you need to replace I’ve got a good condition used one you can have. Just cover the shipping cost. I removed it last year when I got rid of the Hynautic system and installed my all electric system. For that matter, I have the complete Hynautic system if you need other parts. I also had pumps on both engines so you would have power steering if only running one side or the other.

Holy smokes, by all means be on DC auto pilot pump control. Dad always told me, damn the toilet and AC. Take care of the ice maker and the auto pilot. Never want to be without.

Where is the AP pump? You differentiate between that and the engine driven hydraulic steering pump. If the AP pump is anywhere near the helm, that's where the noise is coming from. Flex hoses may help, but I've heard the pumps resonate through the structure they're mounted on.
If the helm were bypassing fluid driven by the AP pump, the wheel should be turning as the AP actuates.

Look forward to all results. Some of us old dawgs may still learn some things.

SeaMar in Seattle has a Greg Hilborn working that knows Hynautic.
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