How to Bleed SeaStar Hydraulic Steering

Bleeding or purging a SeaStar hydraulic steering system is easy to do, but requires two people, so make sure you have an assistant on hand to help you out.

NOTE: This guide is for bleeding/purging a SeaStar single helm, front mount cylinder system or single helm, side mount/splashwell mount system. Multiflex brand hydraulic steering components compatible with SeaStar parts (as seen above) will also be shown.

* All diagrams courtesy of SeaStar Solutions

Step 1 – Preparation 

To purge the hydraulic steering, you’ll be putting hydraulic fluid into one end of the system and draining it out of the other end. 

Therefore, you’ll need something to add the fluid into the helm pump, and something to catch the fluid being expelled from the steering cylinder.

PRO TIP – Cut off the bottom of an old SeaStar hydraulic fluid bottle, then turn the bottle upside down and suspend it above the helm pump. Connect the bottle and helm with a filler tube to establish a gravity feed system. The gravity feed can be continuously topped off by pouring new hydraulic fluid into the cutaway end of the upturned bottle.You can use full bottles of hydraulic fluid instead of a gravity feed system, but you’ll have to change the bottles, and it’s a lot more labor intensive. Any old container can be used to catch the fluid expelled from the steering cylinder.

Step 2 – Fill the Helm Pump

Fill the helm pump with hydraulic fluid before connecting the filler tube. It’s much easier to fill the helm this way, and it reduces the possibility of air becoming trapped in the helm pump. Once the helm pump is full, connect the gravity feed system to the helm via the filler tube. If you’re not using a gravity feed system, connect a new bottle of hydraulic fluid to the helm pump with a filler tube.

PRO TIP: Use a SeaStar filler kit as the filler tube. The kit screws snugly into the bottle at one end and the helm at the other, which means there are no leaks, drips, or mess to clean up.

Step 3 – Extend One Side of the Cylinder Steering Rod

With the helm pump full and the gravity feed system topped off, turn the steering wheel in one direction until the steering cylinder rod has fully extended.

• Turning clockwise with a front mount cylinder system will cause the rod to extend starboard, and vice-versa.
• Turning clockwise with a side mount/splashwell mount cylinder system will cause the rod to move in a port direction, and vice-versa.

Once the rod is fully extended, your helper should open the bleeder on the same side of the cylinder that the rod is extended from, and position a container beneath the bleeder hose.

Step 4 – Bleed the First Side of the Steering System

Have your assistant hold the cylinder rod to prevent it from sliding back into the cylinder.

PRO TIP: Don't use grips or pliers to hold the cylinder rod, as those may damage it. Only hold the rod by hand.

While your helper holds the rod, steadily turn the steering wheel in the opposite direction to which you originally turned it. This will begin to draw new hydraulic fluid from the gravity feed into the helm pump. As the new fluid enters this side of the system, the old fluid – and any air – will bleed out of the open bleeder and into the container.

PRO TIP: Keep an eye on the gravity fill system, and continually top it off. Never allow the gravity feed to run dry, because air will enter the hydraulic system and the entire purging process will have to be restarted.

Continue turning the steering wheel until no more air bubbles are coming from the bleeder, and only fresh clean hydraulic fluid is bleeding through. As you continue to turn the wheel, your assistant should now close the bleeder and release the cylinder rod.

Step 5 – Extend the Other Side of the Cylinder Steering Rod

Keep turning the wheel until the steering cylinder rod on the other side becomes fully extended.

• Turning counter-clockwise with a front mount cylinder system will cause the rod to extend port, and vice-versa.
• Turning counter-clockwise with a side mount/splashwell mount cylinder system will cause the rod to move in a starboard direction, and vice-versa.

Once the rod is fully extended, your helper should open the bleeder on the same side of the cylinder that the rod extended from and should position a container beneath the bleeder hose.

Step 6 – Bleed the Second Side of the Steering System

Repeat Step 4 by having the helper hold the cylinder rod to prevent it from moving, while you turn the steering wheel in the opposite direction from which you just turned it. This time you’re drawing new hydraulic fluid through this side of the hydraulic system and purging the old fluid out of the open bleeder into the container.

PRO TIP: Remember to constantly monitor and top off the gravity fill system.

Continue turning the wheel until no more air bubbles are coming from the bleeder, at which point the helper should close the bleeder and release the cylinder rod.

Step 7 – Check the Steering System

Turn the steering wheel to full lock in one direction, and then apply additional force to pressurize the system. Keep pressure on the wheel while your assistant checks all the hydraulic connections and fittings for leaks. Correct any leaks that are found. Next, turn to the lock in the opposite direction and repeat the process.

PRO TIP: Watch the fluid level in the helm pump as you apply pressure at hard lock. A drop in fluid level indicates there is still air in the system and it must be bled again.

Purge Complete

Once the purge is complete, make sure the helm pump is filled with hydraulic fluid right up to the base of the filler hole.

PRO TIP: SeaStar recommends that all helm pumps are filled to the bottom of the filler hole, and that the fluid in horizontally mounted helms never falls lower than 1/4" from the filler hole, and fluid in helms mounted at 20° (or with a vertical wheel shaft) never falls lower than 1/2" of the filler hole.

The hydraulic system is now fully purged of all the old fluid and any trapped air. Don’t forget to repay your assistant for helping you out, perhaps by trying out the newly bled system with a day’s fishing trip.