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Old 17-07-2009, 20:27   #1
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Location: NY, USA
Boat: Pearson 424, 42' - Kismet
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Help! Simrad RPU 160 install/bleeding

I was wondering if anyone could give some much needed advice-

I have installed my new autopilot system, and am finishing with
the hydraulic arm/pump. The arm is the one the boat came with (seemed to work fine with the old unit) and I'm installng the new rpu160 pump with it.

So, I mounted the unit as per the instructions, and connected the two
couplings to the arm, and the center one to an expansion tank above the pump.

So, according to the instructions, it appears I'm suppsed to bleed the system by letting it draw oil from the tank, and loosen the couplings
at the hydraulic arm to allow the air to escape.

Unfortunately I tried to do this, and no fluid was drawn into the
arm/tubes. So I figured that maybe I needed to get some fluid in first
and it might draw it through better. So I closed the arm,
disconnected a coupling on the pump side, and let it draw the fluid right out of the bottle. At this point it happily pulled the fluid into the hose and
hydraulic arm. Si I connected it back up and tried to move the wheel to
cause more suction on the other side and fill the whole system.

Unfortunately, I couldn't move the wheel much, as I then realized the pump
isn't letting any oil pass throgh it when you turn the wheel. I must
be missing something, but the old pump I had would pass the oil from one side to the other, and draw or deposit into the tank as needed.

Has anyone installed one of there before? I'm wondering if there is some bolt
or screw I need to remove to let it work properly? Does the unit need to be powered on for some reason? (obviously that won't work as I need to be able to steer the boat with the autopilot off!). Or have I bought the wrong unit? (I hope not!). Or is something else afoot here?

I'm open to all suggestions! Thanks for reading this!

Any advice would be much appreciated here.
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Old 21-07-2009, 08:54   #2
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I presume that you have this Simrad manual

“... 5.1 Oil filling and bleeding
When installing a pump unit, it is recommended that the whole system be emptied and refilled. Use a well known oil of a viscosity meeting the specification of the steering gear manufacturer.

Start by opening all stop cocks in the pipes leading to the pump unit.
Simultaneously fill the steering wheel pump with oil whilst turning the wheel itself, back and forth.
Proceed by opening the couplings at the rudder cylinder whilst still turning the wheel, this will assist in creating pressure within the system, continue until clean oil is seen at the couplings.
Now tighten the couplings.
Then open the 3 couplings on outlet A, B and C on top of the pump unit, and repeat the same procedure ...”
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

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Old 21-07-2009, 11:28   #3
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Look very closely at Figure 4-5 in the manual, and make sure that you have connected up the rpu160 like the diagram shows (don't worry about the expansion tank for now). It should not be difficult to turn the wheel unless the rudder has hit the limit stops.

The theory is that the steering wheel drives a pump which pushes the rudder cylinder back and forth, and there are lock valves in the steering wheel pump which keep rudder pressure (or rpu160 pressure) from pushing back on the wheel. You then install the rpu160 in parallel with the original pump, so it can push the cylinder back and forth when its motor runs. The rpu160 also has a valve system in it which prevents leakage across its pump--otherwise when you turned the steering wheel pump, the fluid you were pumping would leak across the rpu160 and the rudder wouldn't turn.

If you have installed the rpu160 correctly, then if you close the three stop cocks at A, B, and C you have removed it from the system, and you should be able to bleed and operate your steering wheel normally to make sure that those parts are working properly. You can then open the stop cocks and bleed the rpu160 part of the system, using your steering wheel and its reservoir as the pump to fill the lines. You should then make sure that all air is out of the rpu160 system by using the rpu160 to move the cylinder back and forth.

The use of a separate expansion tank for the rpu160 is a little trickier, because you need to keep it at the same height as the steering wheel expansion tank.
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