How to Bleed and Replace Brake Fluid on a 2015 Polaris Sportsman 850 SP

Shop parts for a 2015 Polaris Sportsman 850 SP ATV.

This step-by-step MotoSport guide covers a complete brake fluid change and bleed for a 2015 Polaris Sportsman 850 SP. Follow these instructions carefully, use proper safety gear, and dispose of old fluid responsibly. If you aren't comfortable performing brake work, have a qualified technician do it.

What you’ll need

  • DOT 4 brake fluid (Polaris specifies DOT 4 for the Sportsman 850 SP)
  • Clear plastic tubing that fits the bleed nipples
  • Catch bottle for old fluid
  • Brake bleeder kit or hand vacuum pump (optional but speeds the job)
  • Wrenches for bleed nipples (typically 8mm or 9mm)
  • Clean rags and isopropyl alcohol
  • Torque wrench (for caliper bolts if you remove wheels)
  • Jack/stands or a lift to get wheels off the ground securely
  • Latex or nitrile gloves and eye protection

Model notes for the 2015 Sportsman 850 SP

  • The Sportsman 850 SP uses DOT 4 brake fluid; never mix with DOT 3 or silicone fluids.
  • Front and rear braking systems are separate circuits. Bleed each circuit independently.
  • The front master cylinder reservoir is on the handlebar assembly; the rear master cylinder reservoir is located near the foot controls/rear brake pedal area.
  • ABS is not present on most 2015 Sportsman 850 SP models; if your model has an ABS module, consult a dealer before bleeding to avoid unintended pump cycles.
  • Brake lines run through common chassis locations that can be damaged by aggressive cleaning or over-torquing fittings — inspect hoses for cracks, chafing, and corrosion while servicing.

Preparation

  • Work on a flat, stable surface. Secure the ATV with the parking brake and wheel chocks if needed.
  • Wear gloves and eye protection. Brake fluid will damage painted surfaces & plastics; cover body panels with rags or tape.
  • Clean around reservoirs and bleed nipples with isopropyl alcohol so you don't introduce debris.
  • Remove wheels if you need better access to calipers. Support the machine with stands or a lift rated for ATVs.

Step 1 – Inspect and top the reservoirs

Open the front and rear brake reservoirs. Clean the caps and surrounding area before opening. Inspect old fluid color – dark or contaminated fluid warrants a full change. Keep the reservoir level above the minimum during bleeding to avoid introducing air.

Step 2 – Flush old fluid (basic method)

  • Siphon old fluid from the reservoir and discard. Fill with fresh DOT 4 to the full mark.
  • Work one brake circuit at a time: front circuit (both front calipers) and rear circuit.
  • Start with the circuit that is farthest from the associated master cylinder. For the front reservoir, that typically means the caliper farthest from the handlebar master cylinder; for rear, bleed the rear caliper circuit after topping its reservoir.

Step 3 – Bleeding procedure (pump & hold or vacuum method)

Use either the traditional pump-&-hold method with a helper or a hand-held vacuum/pressure bleeder for a one-person job.

Pump-&-hold method:

  1. Attach clear tubing to the bleed nipple and place the other end in a catch bottle partially filled with a little fresh fluid to prevent air being drawn back.
  2. Have a helper slowly squeeze the brake lever or pedal several times and hold pressure.
  3. Open the bleed nipple about a quarter to a half turn to let fluid and bubbles flow into the tubing, then close the nipple before the helper releases pressure.
  4. Repeat: pump, hold, open, close, and top the reservoir as needed until the fluid runs clear with no air bubbles.
  5. Proceed to the next caliper in the correct sequence (farthest first), keeping the reservoir full throughout.

Vacuum bleeder method:

  1. Attach the vacuum pump to the bleed nipple with the clear tubing and place the end in a bottle of fluid.
  2. Open the bleed nipple and pull until fresh fluid with no bubbles flows; close the nipple while the vacuum is maintained.
  3. Top the reservoir as needed and repeat for each caliper in sequence.

Bleed sequence guidance

  • Bleed the caliper farthest from the associated master cylinder first, then the next-farthest, finishing with the nearest.
  • For the front circuit this usually means right-front then left-front or vice versa depending on master cylinder placement — visually confirm line routing on your ATV and pick the caliper farthest from the reservoir first.
  • For the rear circuit there is typically only one rear caliper to bleed.

Step 4 – Final checks

  • Once all air is removed and fresh fluid runs clear, tighten bleed nipples to a snug position. Wipe clean any spilled fluid.
  • Refill reservoirs to proper level and reinstall clean caps. Ensure reservoir diaphragms and caps are in good condition to prevent contamination.
  • Operate the brake controls several times – they should feel firm with no sponginess. If soft, repeat bleeding until firm.
  • Inspect for leaks at fittings, banjo bolts, and bleed nipples. Torque fasteners to manufacturer specs if you removed them (consult service manual for exact values).

Post-service testing

  • With the machine still on stands, apply brakes repeatedly to confirm consistent pressure.
  • Lower the ATV, test at slow speed in a controlled area to ensure braking performance is restored before normal riding.

Maintenance tips specific to the Sportsman 850 SP

  • Replace brake hoses if you see cracking, swelling, or soft spots. OEM replacement hoses are weather-resistant and routed to avoid pinch points.
  • Keep a small spare bottle of DOT 4 on hand for top-offs during trail use — do not mix brands in service, but topping with the same specification is acceptable in emergencies.
  • If your Sportsman has accessory racks or skid plates installed, check that they don't rub on brake lines when fully loaded or during suspension travel.
  • Regularly inspect caliper pins and slide surfaces for corrosion & debris so braking remains even across pads.

Safe disposal

Collect used brake fluid and take it to a local hazardous waste or recycling center. Do not pour it down drains or on the ground.

Troubleshooting

  • Persistent spongy brake lever/pedal after repeated bleeding likely indicates a leak, collapsed hose, or internal master cylinder issue — stop and inspect.
  • If you introduce air or run the reservoir dry, repeat the full bleed sequence for that circuit.
  • Contaminated fluid that smells or appears milky should be fully flushed from the system; consider replacing rubber components if contamination is severe.

Performing a full brake fluid change and bleed on your 2015 Polaris Sportsman 850 SP ensures consistent stopping power and helps prevent corrosion in the system. For replacement parts designed to fit your exact MMY, visit the MotoSport parts link above to find master cylinders, hoses, caliper kits, pads, and DOT 4 fluid options specific to this machine.

Related Shopping Categories

Shop Brake Fluid for a 2015 Polaris Sportsman 850 SP ATV.

Shop Brake Bleeders for a 2015 Polaris Sportsman 850 SP ATV.

Shop Brake Pads for a 2015 Polaris Sportsman 850 SP ATV.

Shop Brake Lines for a 2015 Polaris Sportsman 850 SP ATV.

Shop Brake Tools for a 2015 Polaris Sportsman 850 SP 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.