How to Bleed & Replace Brake Fluid on a 2018 Honda TRX500 Rubicon 4X4 POWER STEERING (FM6)

Shop parts for a 2018 Honda TRX500 Rubicon 4X4 POWER STEERING (FM6) ATV.

This MotoSport-exclusive how-to covers replacing the brake fluid and correctly bleeding the hydraulic brake system on the 2018 Honda TRX500 Rubicon 4X4 POWER STEERING (FM6). Follow these steps carefully to maintain stopping performance and safety. Work in a clean, well-lit area and use quality DOT 4 brake fluid unless your owner’s manual specifies otherwise.

What you’ll need

  • DOT 4 brake fluid (new, unopened)
  • Clear plastic tubing that fits snugly over bleeder nipples
  • Brake bleeder bottle or clean catch container
  • Wrench set (bleeder wrench sized to caliper nipples)
  • Rubber gloves, safety glasses
  • Clean rags and isopropyl alcohol for cleaning
  • Jack / stands or ramps to lift the ATV securely (if required)
  • Assistant for manual pump bleeding, or a hand/vacuum pressure bleeder

Model notes specific to the TRX500R_PS (2018)

  • The master cylinder and reservoir are located near the handlebar area; both front and rear brakes share the system. Keep the reservoir cap clean to prevent contamination.
  • Because this model has power steering, take care to avoid cross-contamination between brake fluid and power steering fluid. Brake fluid will damage paint and rubber parts for the PS system.
  • Calipers on this ATV use external bleeder nipples. Use caution not to round the nipple hex — use the correct wrench size and short, steady turns.
  • If the ATV shows persistent spongy brakes after bleeding, suspect internal master cylinder leakage, contaminated lines, or caliper seals — further diagnosis may be needed.

Preparation

  • Park the ATV on level ground. Put it in park and block the wheels.
  • Clean the reservoir cap and surrounding area before opening.
  • Check and note existing fluid level and color. Dark or contaminated fluid indicates it needs replacement.
  • If lifting the ATV, support it solidly so wheels can turn freely during bleeding.

Recommended bleeding order

Start with the wheel farthest from the master cylinder and work toward the closest. Typical order for a TRX500 is: rear (farthest) first, then the opposite rear/front pattern toward the front nearest the master cylinder. If uncertain, identify the farthest caliper visually and use a farthest-to-nearest sequence.

Step-by-step procedure

  1. Remove reservoir cap and diaphragm. Wipe area clean. Keep the reservoir topped up with fresh DOT 4 fluid throughout the procedure to avoid introducing air.
  2. Attach clear tubing to the bleeder nipple on the first caliper and submerge the other end in a small amount of fresh fluid in your catch bottle to prevent air from being drawn back in.
  3. Have an assistant pump the brake lever/pedal several times and hold firm while you open the bleeder nipple about 1/4 turn. Fluid and air will flow into the tubing. Close the nipple before the assistant releases the lever/pedal. Repeat until the expelled fluid is clean and free of bubbles.
  4. After each cycle, top up the master reservoir immediately. Do not let the reservoir run low during bleeding.
  5. Repeat the process for each caliper/wheel in the chosen order until all lines flow clear and bubble-free fluid. If using a vacuum or pressure bleeder, follow the tool manufacturer’s procedure but still keep the reservoir topped up.
  6. Once finished, tighten bleeder nipples to specified snugness (hand tool fit, then a small additional turn — avoid over-torquing). Wipe any spilled fluid and reinstall reservoir diaphragm & cap securely.

Flushing the system (complete fluid replacement)

To replace all fluid, continue bleeding each wheel until the fluid flowing out matches the color and clarity of the fresh fluid you’re adding at the reservoir. If the reservoir holds only a small amount, refill several times during the sequence until the entire circuit is exchanged.

Finishing steps & safety checks

  • Confirm pedal/lever firmness with the engine off. The pedal should be firm and not sink to the floor. If soft, repeat bleeding or inspect components.
  • Inspect calipers, hoses, fittings, and master cylinder for leaks.
  • Clean any spilled fluid from painted surfaces immediately; brake fluid can damage paint and plastics.
  • Test ride at slow speed in a safe area to verify braking response before normal use. Avoid heavy braking until you’re confident the system is working correctly.
  • Dispose of old brake fluid per local hazardous-waste regulations.

Troubleshooting

  • Persistent soft lever/pedal after thorough bleeding: suspect internal master cylinder seal failure or caliper piston seizure. Consider rebuild/replacement.
  • Bubbles continue despite correct procedure: check for leaking fittings, cracked hoses, or a warped reservoir cap that allows air ingress.
  • Brake drag after bleeding: make sure bleeder nipples are fully tightened and caliper pistons return freely. Check for hydraulic lock or stuck pistons.

Maintenance tips

  • Replace brake fluid every 1–2 years depending on use and exposure to water/contamination; severe use (mud, water crossings) calls for more frequent changes.
  • Keep a small sealed bottle of DOT 4 in your toolbox for topping up; never mix brake fluid types without confirming compatibility.
  • When working around the power steering unit, keep brake fluid away from PS components, seals, and paint.

Follow these steps carefully to restore brake performance on your 2018 TRX500 Rubicon PS. If you encounter uncertainty about master cylinder condition or persistent issues after bleeding, seek professional service to ensure safety.

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Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.