Hynautic Steering Issue

[oscarvan]

There's more going on but I don't want to over complicate it.

Short version is that a new autopilot pump was installed, and as a result I had no steering, or more correctly, sketchy steering at lower helm. Many turns some movement..... On a sea trial at WOT, but i digress. Air in the line.

Yes I have the instructions and I unscrewed the pressure relief valves as per procedure, BUT..... even after doing that the upper helm is still moving the rudder and limited to it's 4-5 turns, in other words it's not by passing allowing me to do the 40 turns and move the fluid through the system. Upper helm is working correctly though.

My next step is to crack the lines at the lower helm, but I am still scratching my head as to why I can't bypass the piston......

[Captain Ralph]

All Hynautic bleeding is tone at the T block.
Reservoir full and under pressure, open the relief screws and turn, turn, turn.

No line cracking.

Yes, the rudder may move but the wheel will not stop and keep rotating.
If it does stop, the screws are not fully backed off or a bad T block.

[krush]

What Mr Ralph posted is exactly correct. Bleeding a hynautic of air is the most stress free and simple hydraulic bleeding procedure you will ever encounter.....provided the relief valves are opening.

Only open one relief valve at a time.

[oscarvan]

One at a time? That's not what the book says.....

When you say "T-Block" do you mean the MSV-21, shown below?

There are bleed nipples on the piston, I don't see any on the MSV21

[jmooney]

No fluid is bled out of the system. Opening the relief valves allows fluid to go back to the reservoir taking air with it .

[oscarvan]

OK after talking to the man who has installed more Hynautic systems than he can remember it appears I have a sticky valve in the MSV21. I will replace.

[Captain Ralph]

One at a time? That's not what the book says.....

When you say "T-Block" do you mean the MSV-21, shown below?

There are bleed nipples on the piston, I don't see any on the MSV21

Yes, My bad term.
Those brass screws, screw up about 3/4". they do not come out but will stop at end of travel.
Then turn,, turn,, turn the steering wheels and AP pump while checking on fluid level and pressure.

Yes, later cylinders had bleed nipples. Unless that ram was removed, I would not worry about going there.

[Captain Ralph]

OK after talking to the man who has installed more Hynautic systems than he can remember it appears I have a sticky valve in the MSV21. I will replace.

If one steering pumps is working and the others not, I disagree.
The MSV21 is common to all 3 of your heads. If one of the three has an issue at that pump,, of course after bleeding all well.

[Captain Ralph]

Now, since all of this started when the AP pump was installed,
AND I'm sure service valves were installed,
have you closed off the AP pump and checked for problems?

Because it's new, does not guarantee it is fault free.

[Pascal]

It s always on survey day. Reminds me of last year when I was coming back down the channel at 20kts and lost steering altogether on the 84. Slowed down using asymmetrical thrust to stay between the stick. Nobody noticed something was wrong turned out to be a broken bronze tiller arm

Anyway… if the upper helm is working it’s easy because of how the pump was plumbed or air got in the lower helm somehow. Have you tried basic purging by turning the lower helm until it stops then back the other way? That has always cleared air bubbles for me