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Tips for Bleeding the Hydraulic System

Basic Bleeding Procedure


  1. Start at the helm closest to the steering cylinder (multi-helm only)

  2. Remove the fill plug and install hose fitting and hoses

  3. Wrap an oil absorb pad around the helm to prevent leaks

  4. Ensure any other helms in the system have non-vented plugs installed, or leaks will occur

  5. Connect hoses to the steering cylinder and loosen the bleed fittings by one turn

  6. Connect 12V power

  7. Switch on purge and check for leaks

  8. Turn the steering wheel clockwise until the steering ram fully extends, and continue turning slowly for at least 30 seconds or until no bubbles are visible in the cylinder hose

  9. Repeat counterclockwise as above

  10. If there are additional helm stations, repeat the above steps as necessary

  11. Set autopilot to Dealer Mode* and use 'Verify Steering Direction' to operate the pump in each direction for at least 30 seconds

  12. Disconnect hoses and power cables. Tighten bleed fittings, verify fluid level in helm, and install plug

  13. Operate the helm in both directions and check for smoothness and positive end stops

  14. Operate autopilot and verify that the rudder moves smoothly

*To put the autopilot into dealer mode follow these steps:

From the GHC™ 20autopilot controller: Press the Menu Button >  Set Up > System > System Information Press and hold the center soft key until Dealer Mode appears above it.

From the GHC™ 50 autopilot controller:

The GHC 50 autopilot controller does not require extra steps to access Dealer Mode. 

From the main screen, press the three dots > Autopilot Setup > Autopilot Installation, and press OK to the caution message. The following options display under Autopilot Installation. 

  • Wizards

  • Speed Source Setup

  • Steering system Setup

  • Compass Setup

  • Autopilot tuning

  • Restore Defaults


Tips for bleeding the hydraulic system


Performing any changes to a hydraulic system requires bleeding the system. Check with the helm manufacturer's owner's manual for brand-specific directions on bleeding the steering hydraulics on the vessel.

  • Use the proper amount of hydraulic fluid when installing the autopilot

  • The autopilot is considered the lowest station in the hydraulic steering system

  • Do not use Teflon tape on any part of the hydraulic system

  • If replacing the pump and contamination of the hydraulic fluid is suspected, flush the old hydraulic fluid and replace it with new fluid

  • If there are bleeding issues reusing hydraulic fluid, try using a fine mesh filter such as those for gasoline. A Power Purge (Seastar) or the Bubble Buster (Uflex) system has built-in screen filters on the pump pickup line

  • When performing the Autotune Steering direction, if it does not go hard over and give a "Pump Stall" error, air is still in the lines; consider using a power purge to bleed the system

Several steering systems and helms can quickly be bled by hand. Meanwhile, more complex systems may require additional equipment, such as a power purge, so it is recommended to seek a certified Garmin Marine Installer


Additional Considerations


How many helms are on the boat? 

  • In a multiple helm system, use a power purge system as air can get trapped in the lines of complex systems and not easily hand-bled

What type of fluid is used? Automatic Transmission Fluid (ATF) is not recommended.

  • ATFs are not designed for hydraulic systems; ATFs are designed for lower-pressure and lower-temperature systems

  • ATF does not have the viscosity that hydraulic fluid does

  • ATFs have detergents in them and are often used for cleaning an engine

  • The color can identify ATF; it's either green or red. Hydraulic fluid should be clear or milky in color

  • Does the hydraulic fluid have the correct viscosity oxidation stability, and is foaming resistant? A higher operating temperature range will aid in sealing O-rings better, with lubrication, and will perform better in the hydraulic system

What is the steering fluid level at the helm?

  • To check this, remove the filler plug on the helm. View into the hole hydraulic fluid should be visible; check the helm manufacturer's recommended level, as these can vary. When adding an Autopilot pump, add additional hydraulic fluid to the system

Where and in what position is the pump mounted?

  • If mounted in the incorrect position (upside down, vertically with the manifold pointed down), air can become trapped

How many turns does the manufacturer list as hard over? How many turns is it going? 

  • If it's going past the manufacturer-recommended turns, air is in the lines

  • It should come to a hard stop when performing the turns in the bleeding process; if it's soft or slips, there is either air in the lines or not enough fluid in the reservoir

Was hydraulic fluid reused? It is common to reuse hydraulic fluid; however, if there are issues with bleeding the system, replace the fluid and use a Power Purge (Seastar) or Bubble Buster (UFlex) for bleeding. Both of these systems have a built-in filter in the pump pickup line.