How do I bleed the brakes on my boat trailer?

Bleeding boat trailer brakes removes air from the hydraulic system, ensuring proper braking power. Air in the lines causes a spongy pedal or actuator feel, reducing safety on the road.

Step-by-Step Boat Trailer Brake Bleeding

1. Prepare the Trailer
   • Detach the trailer from the tow vehicle.
   • Block the wheels securely.
   • Fill the master cylinder in the actuator with the recommended brake fluid (DOT 3 or DOT 4 — check your actuator cap). Keep it topped off during the process.
2. Start with the Farthest Wheel
   • Open the bleeder screw on the brake caliper or wheel cylinder farthest from the actuator.
3. Apply Pressure
   • Push the actuator slide in firmly and hold it.
   • While pressure is held, open the bleeder screw to allow fluid and air to escape.
4. Close and Release
   • Tighten the bleeder screw, then release the actuator slide.
   • Repeat this process until only fluid flows out (no air bubbles).
5. Work Inward
   • Move to the next farthest wheel and repeat until all brakes are bled.
6. Bench-Bleed New Actuators
   • If installing a new actuator, it should be bench bled (pre-bled) before connecting to the hydraulic line.
7. Final Check
   • Refill the master cylinder as needed throughout the process.
   • When finished, check for firm braking action and test the trailer at low speeds before towing.

⚠️ Boat Trailer Owner Tips

Saltwater Use: Replace brake fluid annually, since saltwater increases the chance of moisture intrusion.
Inspect While Bleeding: Look for leaks at fittings, calipers, or lines.
Disc vs. Drum Brakes: The process is the same, but disc brakes are easier to inspect for leaks and pad wear during service.

Watch the Process:

How to Manually Bleed Boat Trailer Brakes (Dexter Video Guide)

How to Power Bleed Boat Trailer Brakes (Dexter Video Guide)

*These videos from Dexter Axle demonstrate the correct procedure for bleeding hydraulic boat trailer brakes.