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Old 28-01-2016, 07:05   #1
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Hydraulic Autopilot Repair

I recently repaired the hydraulic ram for my autopilot and learned some lessons that might be good to share. My autopilot electronics are Simrad that I installed 10 years ago, but the hydraulics are Lecomble & Schmitt (France) probably installed in late 90's. I believe most hydraulic systems work the same way so, hopefully, this may help others with the same problem. Symptoms: The electronic components appeared to be working normally, but the rudders/helm were moving erratically. The 12V DC pump was running, but the helm was not moving or moving with a jerky motion. The autopilot would alarm since it could not correct to course.

The first step was to isolate whether the problem was with the hydraulic pump or with the hydraulic ram. A friend helped me diagnose this and the solution was to turn on the autopilot with the rudder position indicator disconnected (small mechanical device attached to rudder quadrant). This procedure activated the solenoid on the hydraulic pump to prevent hydraulic oil from free flowing from one side of ram to another. Disconnecting the rudder position indicator allowed us to turn the helm without the autopilot brain trying to correct back to course. In theory, this set up should have hydraulically locked the helm. With the helm "locked" we were able to slowly turn the helm even though it should have been locked by hydraulic fluid in the ram. We concluded that hydraulic fluid was leaking past the seals in the piston of the hydraulic ram and the ram was the culprit.


I took the ram to a hydraulic repair specialty shop in Tampa and they replaced all the seals (piston and seals on both ends) and leak checked the ram. I reinstalled the ram this week and bled both the hydraulic pump and the ram. The autopilot is working normally again. The cost of repair was $125 which was a great deal compared to the cost of a new ram $2,600.


I also had an early symptom of this problem that I didn't recognize until now. When the temperature was cold (40's F) the AP wouldn't hold course and would alarm. After it warmed up it would work normally. I believe the piston seals in the ram were leaking due to cold, but when they got warmer they expanded and worked normally. After a couple years the temperature threshold climbed until it was an "all temperature problem."
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Old 28-01-2016, 07:34   #2
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Re: Hydraulic Autopilot Repair

We had similar systems not long ago with our AP. The ram was loose and leaked most of the fluid into the bilge. Replaced and bled and all is well. What did you use for fluid? L&S recommend ISO 22 but we were unable to find that grade. We currently have ISO 15 in it, but others have also recommended red fluid ISO 30.
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Old 28-01-2016, 09:19   #3
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Re: Hydraulic Autopilot Repair

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We had similar systems not long ago with our AP. The ram was loose and leaked most of the fluid into the bilge. Replaced and bled and all is well. What did you use for fluid? L&S recommend ISO 22 but we were unable to find that grade. We currently have ISO 15 in it, but others have also recommended red fluid ISO 30.
Monte, I have been using NAPA hydraulic jack oil, pn 1541, for several years. I asked the guy in the hydraulic shop if that was OK or should I be using something different. He said the NAPA oil was fine and it was a very low viscosity oil. I don't know the ISO number and couldn't find it. He also said Dexron would also work. (I assume he was talking about Dexron transmission fluid.)
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Old 31-03-2016, 11:43   #4
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Re: Hydraulic Autopilot Repair

Any help here would be greatly appreciated.

More Autopilot issues here. My Autonav Type 2 hydraulic pump started leaking. I bought an Octopus Type 2 rated replacement pump and installed it. Now, I, and two technicians (one, the hydraulic pump expert, and two, the Raymarine technician), are stumped. The pump doesn't respond properly (not even close), to the EV400 AP commands. The hydraulic technician rechecked the installation and damped down the fluid flow volume setting. The Raymarine tech scratched his head. No improvement.

I'm taking matters into my own hands now--it can't be that difficult and I want to know how to fix/repair/correct the A.P. while I'm "out there" in the middle of the Pacific this summer.

Thank you--I'm looking forward to your replies.
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Old 31-03-2016, 14:15   #5
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Re: Hydraulic Autopilot Repair

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Any help here would be greatly appreciated.

More Autopilot issues here. My Autonav Type 2 hydraulic pump started leaking. I bought an Octopus Type 2 rated replacement pump and installed it. Now, I, and two technicians (one, the hydraulic pump expert, and two, the Raymarine technician), are stumped. The pump doesn't respond properly (not even close), to the EV400 AP commands. The hydraulic technician rechecked the installation and damped down the fluid flow volume setting. The Raymarine tech scratched his head. No improvement.

I'm taking matters into my own hands now--it can't be that difficult and I want to know how to fix/repair/correct the A.P. while I'm "out there" in the middle of the Pacific this summer.

Thank you--I'm looking forward to your replies.
Clady, Sorry this isn't working for you. I have a few questions to for troubleshooting the problem. Can you isolate the problem to electrical or hydraulic problem? When you say the pump doesn't respond properly, can you be more specific? Does the pump run and sound the same with a turn to port or starboard? Is the wiring diagram the same for both pumps? Does the rudder post turn in the correct direction?
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Old 31-03-2016, 14:18   #6
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Re: Hydraulic Autopilot Repair

Forgot to mention bleeding the system. If you have any air bubbles in the pump, lines or ram, you will erratic operation. You need to bleed the pump, lines and the ram.
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Old 31-03-2016, 14:54   #7
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Re: Hydraulic Autopilot Repair

Yes, it is erratic. starts and stops, drifts--feeble operation. Air in the system?
It is just a reversing pump. Two wires hooked up to the pump, that's all.
The EV 400 system doesn't require any rudder reference sensors. it's all electronic command operation and parameters with the Raymarine EV400 computer.
I appreciate your suggestions/possible answers.
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Old 31-03-2016, 15:51   #8
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Re: Hydraulic Autopilot Repair

Quote:
Originally Posted by CLady View Post
Yes, it is erratic. starts and stops, drifts--feeble operation. Air in the system?
It is just a reversing pump. Two wires hooked up to the pump, that's all.
The EV 400 system doesn't require any rudder reference sensors. it's all electronic command operation and parameters with the Raymarine EV400 computer.
I appreciate your suggestions/possible answers.
Sorry if I've misunderstood your meaning but you seem to say bleeding isn't a possible cause?

Raymarine forum gives a bleeding procedure here.

Bleeding Autopilot Hydraulic System - Raymarine Technical Forum
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Old 31-03-2016, 18:02   #9
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Re: Hydraulic Autopilot Repair

Quote:
Originally Posted by CLady View Post
Yes, it is erratic. starts and stops, drifts--feeble operation. Air in the system?
It is just a reversing pump. Two wires hooked up to the pump, that's all.
The EV 400 system doesn't require any rudder reference sensors. it's all electronic command operation and parameters with the Raymarine EV400 computer.
I appreciate your suggestions/possible answers.
Clady, Air in the system could cause the symptoms you describe. When I repaired my hydraulic ram and reinstalled it, I thought I did a good job of bleeding the air out of the ram. When I engaged AP it moved erratically and would not hold a course. I discovered that oil level in pump had gone down. I refilled and bled the pump and ram again. After that it worked great.

Another thought: could the seals on the hydraulic ram piston be leaking? That was my situation. Fluid did not leak out of end-cap seals so there was no visible fluid, but fluid was bypassing the piston seals instead of moving the ram.

Good luck!
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Old 31-03-2016, 20:52   #10
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Re: Hydraulic Autopilot Repair

Hi SVCattales,
Thank you for the support and reply--so, I'm now looking for details on the beswt way to bleed the components of the system--pump and ram.

You have me also thinking of the poosibility of the seals in the ram giving fluw interna;;y as bnothin shows on the outside.

Thank you! This is helping me get my head into it and not be so overwhelmed.
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Old 31-03-2016, 21:22   #11
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Re: Hydraulic Autopilot Repair

All of the Hydraulic systems I am aware of are bled at the helm through the manual pump. Top up the reservoir to the fill level. Rotate the wheel in one direction to rudder stops. Check oil level, fill as required. Rotate wheel fully in the other direction until rudder stops. Check oil level, fill as required. continue till oil level remains stable after helm movement.

In normal circumstances fully stroking the cylinder(s) in each direction is enough to move any trapped air out of the system through the tank line. In rare circumstances or upon initial installation it may be necessary to crack the fittings at the ports on the cylinder while turning the wheel or initiating the pump to provide oil pressure. Beware of pinch points if attempting to bleed using 2nd method.
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Old 31-03-2016, 21:29   #12
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Re: Hydraulic Autopilot Repair

Thank you a bunch undercutter! That helps clue me in quicker!
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