Changing hydraulic fluid in Simrad autopilot?

[sailah]

Anyone done it? Nothing is wrong with my autopilot but I like changing out fluids for maintenance and I've never done this since I've owned the boat. And to my knowledge it's probably never been done on my boat. I can't find any threads on this even using Google so maybe I'm looking for a problem that doesn't exist.

I have the split hydraulic unit with separated pump and ram connected by hydraulic hoses.

Maybe it's pretty basic I'd just like to be prepared with the knowledge before I let the magic Norwegian whale oil out.

Thx.

[pcmm]

Originally Posted by sailah

Anyone done it? Nothing is wrong with my autopilot but I like changing out fluids for maintenance and I've never done this since I've owned the boat. And to my knowledge it's probably never been done on my boat. I can't find any threads on this even using Google so maybe I'm looking for a problem that doesn't exist.

I have the split hydraulic unit with separated pump and ram connected by hydraulic hoses.

Maybe it's pretty basic I'd just like to be prepared with the knowledge before I let the magic Norwegian whale oil out.

Thx.

Usually the autopilot pump drives the same ram as the regular steering so you just drain the main system and refill. How does the AP overcome the resistance of the main steering ram? If the AP has its own resvoir just drain it and refill it.

[GordMay]

“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.”

5.1 (Page 25) ➥ https://www.simrad-yachting.com/Root..._manual_EN.pdf

[sailah]

Originally Posted by pcmm

Usually the autopilot pump drives the same ram as the regular steering so you just drain the main system and refill. How does the AP overcome the resistance of the main steering ram? If the AP has its own resvoir just drain it and refill it.

I have quadrant steering with cables so no other ram. The autopilot is essentially self contained. Has its own separate steering quadrant arm mounted to rudder post.

The autopilot pump looks like this and the reservoir is on top which is the tank. No obvious drain plugs from the outside. I will look closer and see if there are any bleed screws.

I've bled plenty of motorcycle brakes in my day and for that it's a gravity system with the bleed nipple on the disc caliper.

Just sucking the fluid or draining from the tiny tank won't replace the volume of fluid in the ram. Need to get that fluid either drained or pumped out somehow.

Originally Posted by GordMay

“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.”

5.1 (Page 25) ➥ https://www.simrad-yachting.com/Root..._manual_EN.pdf

Thanks Gord I saw that manual and have it printed out. From the sounds of it they are assuming you are using hydraulic steering and would fill it from the reservoir on the steering wheel, which makes sense from other diagrams. I have cable steering so the only options have to be on either the pump or the hydraulic ram.

It's a fairly simple system and my pump is the high point in the system. My thoughts were to crack open the hydraulic lines leading to the pump in lieu of a bleed nipple. Cycle the ram back and forth to push all fluid out the lines into a catch can. Use a syringe with a hose to suck the fluid out of the pump reservoir if it doesn't automatically drain when I remove the hoses.

Assemble the hoses again, fill the reservoir with new hydraulic fluid and cycle the pump back and forth. Since the pump is the high point, the displaced air will get bled out the reservoir tank. The tank isn't very big and I'm thinking there is far more volume of fluid in the cylinder. Which makes me think of geyers of hydraulic fluid going everywhere and it's a confined space.

[tkeithlu]

I've done it, and I wish my Simrad system was as simple as yours, rather than part of my manual hydraulic steering. Messiest job on earth. Drain it at all the low places, then move it back and forth using the wheel to eject the last bit. Pour in at the top, moving it back and forth until the last bubbles exit. Then run the rudder test on the control head. If it fails because "rudder moves too slowly" then you'still got air in the system.






















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[sailah]

Got it thanks. I'm prepared for messy

[Chuck Hawley]

I have the combined version of your hydraulic autopilot on my Alerion (HLD2000 Mk2L). The autopilot started to act peculiarly and I could not figure it out until I surmised that it was low on hydraulic fluid. I searched all of the literature on the boat for information (installation manual, operating manual) as well as online, but I could not find any information on how to add fluid and bleed the system.

Eventually, I just opened what appeared to be the filler plug on the top of the reservoir and topped off the fluid. Then I ran the helm back and forth to pull fluid into the cylinder and expel the air into the reservoir. I refilled the reservoir and repeated the process several times. Eventually, the reservoir stayed full, and I presume that I was able to remove all of the air.

Since then, the autopilot has worked perfectly.

There is probably a faster or more predictable way to do this, but I could not find any instructions.

Chuck Hawley

[sailah]

Thanks Chuck. As best I can tell this autopilot was installed in the early 2000s. From what I can glean from other maintenance issues I've dealt with, the fluid is most likely original hence the desire to change it out.

Mine has worked flawlessly and part of me says leave well enough alone. But all things work, right up until the time they don't...

I think based on your experience and mine with hydraulics, it should be reasonably straightforward and just a matter of working it back and forth until the bubbles all come out the reservoir.

When I do it, I'll document with pics for future reference.

[tkeithlu]

You're right on, Chuck.. Back and forth stop to stop with the wheel is the way to expell the air you can't bleed out by other means. It can be tiresome with a system like mine, with low spots and long runs, but it eventually works.

[Hickers]

Or wait until the screws holding the pump body to the motor loosen enough to allow all the red fluid to be sprayed across the lazerette then spend hours cleaning up the mess. Refill with spare atf fluid after learning how to put the pump back together in a rocky anchorage. Another item on my check list now!!