How to Bleed and Replace Brake Fluid on a 2008 Yamaha Grizzly 660 4X4

Shop parts for a 2008 Yamaha Grizzly 660 4X4 ATV.

This MotoSport guide covers complete brake-fluid replacement and bleeding for the 2008 Yamaha Grizzly 660 4X4. Follow the steps below for a safe, effective job. Work in a clean, well-ventilated area, keep brake fluid away from painted surfaces, and wear gloves and eye protection.

What you need

  • DOT 4 brake fluid (Yamaha recommendation) – clean, unopened container
  • Socket set, open-end wrenches
  • Bleeder wrench or correct-size box wrench for caliper bleeder screws
  • Clear plastic tubing and a catch bottle (for one-way bleeding)
  • Vacuum or pressure brake bleeder (optional, speeds the job)
  • Clean rags, shop towels, small funnel
  • Brake-clean spray and a small brush
  • Zip ties or clamps to secure tubing
  • Torque wrench (for caliper/line fittings if you plan to remove components)

Model-specific notes for the 2008 Grizzly 660 4X4

  • Hydraulic system: conventional hydraulic calipers with a front master cylinder at the handlebar and a rear master cylinder near the foot brake – no ABS.
  • Master cylinder reservoirs are small translucent plastic; inspect the reservoir cap diaphragm for cracks and replace if degraded.
  • Recommended fluid: DOT 4. Never mix DOT 4 with DOT 5 silicone fluid.
  • Brake line routing on the Grizzly can be snug near the frame; inspect lines for chafing or age cracks while you work.
  • If you see contaminated fluid that is dark or contains debris, flush both front and rear circuits completely and consider replacing flexible hoses if they look swollen or cracked.

Preparation

  1. Park on level ground, engage parking brake, and disconnect the battery negative terminal to avoid accidental starts while working.
  2. Clean around both master cylinder reservoir caps to prevent contamination when opened.
  3. Raise the ATV as needed to access calipers — leave wheels on for normal bleeding unless you need to inspect pads or rotors.
  4. Shake the new DOT 4 fluid container to settle contents, then open carefully.

Full fluid replacement – step-by-step

Use this sequence to replace old fluid with fresh fluid, avoid drawing air into the system, and purge each circuit properly.

  1. Start with the reservoir: remove the cap and diaphragm, then use a syringe or turkey baster to remove as much old fluid as possible from the reservoir. Dispose of used fluid properly.
  2. Refill the reservoir with fresh DOT 4 fluid to the full mark. Keep the cap off while bleeding so you can monitor fluid level.
  3. Bleed order: rear caliper(s) first, then front calipers, finishing at the caliper farthest from its master cylinder. For the Grizzly 660 this commonly means: rear caliper → right front caliper → left front caliper — but verify by locating master cylinders and following the longest hydraulic run first.
  4. Attach clear tubing to the bleeder nipple and place the other end into a catch bottle partially filled with fresh fluid to avoid drawing air back in. Crimp the tubing lightly where it passes under the bleeder wrench to prevent fluid siphoning back if you stop mid-step.
  5. One-person vacuum/pressure method (preferred): connect a vacuum pump to the bleeder nipple or use a pressure bleeder on the reservoir. Pump until you see clean fluid with no bubbles. Keep reservoir topped off during the process.
  6. Two-person manual method: an assistant slowly applies steady pressure to the brake pedal or lever (about half-stroke). Open the bleeder screw briefly (about 1/2 turn), let fluid and bubbles exit into the tubing, then close the screw before the assistant releases the pedal. Repeat until only clear, bubble-free fluid appears. Always close the bleeder before pedal release to prevent drawing air in.
  7. For each caliper, repeat until fluid runs clear and no air bubbles appear. Monitor and top off the reservoir frequently to avoid draining it dry.
  8. After bleeding each caliper, tighten the bleeder screw to the manufacturer's feel — snug but avoid over-torquing. If you removed lines or fittings, torque to spec if known or tighten securely and inspect for leaks under pressure.
  9. When all circuits are bled, fill reservoir to the proper level, reinstall diaphragm and cap, and wipe any spilled fluid from painted surfaces with brake cleaner immediately.

Bench checks and final steps

  • Pump the brake lever and pedal to confirm a firm feel. If the lever/pedal feels spongy, repeat bleeding until firmness is restored.
  • Inspect all bleed screws, banjo bolts, line fittings, and calipers for leaks while an assistant applies pressure. Tighten if necessary.
  • Lower the ATV, road-test at low speed in a safe area to confirm braking performance.
  • Properly dispose of old brake fluid per local regulations; do not pour it down drains.

Troubleshooting tips

  • Persistent sponginess: likely trapped air. Re-bleed using vacuum or pressure method and ensure reservoir never runs dry during bleeding.
  • Contaminated or foamy fluid after bleeding: flush reservoir and lines again; consider caliper rebuild if contamination was severe.
  • Soft pedal only under heavy braking: check for flexible hose swelling. Replace hoses if they expand under pressure.
  • Leaking bleeder screws: replace the screw or use a new crush washer if the fitting is a banjo bolt type.

Maintenance interval & best practices

  • Replace brake fluid every 1-2 years or sooner if the fluid appears dark or contaminated.
  • Inspect brake lines, calipers, pads, and rotors each season — the Grizzly 660 is often used in wet, muddy conditions that accelerate wear and contamination.
  • Always use fresh DOT 4 fluid from a sealed container and avoid reusing old fluid.

Following this MotoSport procedure will restore braking performance and help keep your 2008 Yamaha Grizzly 660 4X4 safe on trail or work duty. If you encounter a complex failure — master cylinder damage, collapsed hoses, or caliper seal failure — consult a qualified technician.

Related Shopping Categories

Shop Brake Fluid for a 2008 Yamaha Grizzly 660 4X4 ATV.

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Shop Brake Pads for a 2008 Yamaha Grizzly 660 4X4 ATV.

Shop Brake Lines for a 2008 Yamaha Grizzly 660 4X4 ATV.

Shop Brake Tools for a 2008 Yamaha Grizzly 660 4X4 ATV.

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.