How to Bleed & Replace Brake Fluid on a 2017 Polaris Sportsman 850

Shop parts for a 2017 Polaris Sportsman 850 ATV.

This MotoSport-exclusive guide walks you through safely replacing and bleeding the brake fluid on a 2017 Polaris Sportsman 850. Follow these steps carefully to maintain reliable braking performance and protect the ABS system and calipers from contamination and corrosion.

What you’ll need

  • DOT 4 brake fluid (Polaris recommends DOT 4 for this model)
  • Clear plastic tubing that fits over bleed nipples
  • Clean catch bottle with a small amount of fresh brake fluid in the bottom to prevent air draw-back
  • Brake cleaner and lint-free rags
  • Open-end wrench for bleed nipples (usually 8 mm)
  • Turkey baster or fluid syringe (for removing old fluid from reservoir)
  • Gloves and eye protection
  • Service manual torque values and bleed sequence reference

Important model-specific notes for the 2017 Polaris Sportsman 850

  • The 2017 Sportsman 850 uses a hydraulic braking system with an optional or integrated ABS module on some trims. If your ATV is equipped with ABS, do not open or attempt to service the ABS unit internals. Bleed the system using the normal caliper bleed nipples only.
  • The vehicle uses DOT 4 fluid. Mixing different fluid types can damage seals and performance — do not use DOT 3 unless specified by your owner’s manual for a temporary emergency top-up.
  • The front and rear master cylinders share a reservoir on some configurations. Keep reservoir clean and capped to avoid contamination from dirt or water while working.
  • Polaris recommends replacing brake fluid every 2 years under normal use; more frequently if riding in wet or humid conditions.
  • Brake lines on older Sportsmans can show wear at fittings; inspect hoses and fittings for cracking, swelling or corrosion while draining the system.

Preparation

  1. Park the ATV on a level surface and engage the parking brake. Turn off the engine and remove the key.
  2. Clean around the brake fluid reservoir cap and surrounding area to keep contaminants out.
  3. Remove the cap and diaphragm; use a turkey baster to remove as much old fluid as possible from the reservoir.
  4. Fill the reservoir with fresh DOT 4 fluid to the indicated level, then loosely reinstall the cap so you can monitor level during bleeding.
  5. Identify bleed nipples at each caliper. The Sportsman 850 typically has a front left, front right, and rear caliper bleed nipples. Refer to your manual for exact locations and the recommended bleeding sequence: usually farthest from the master cylinder first (rear or right front) then closest.

Bleeding sequence & method

For most 2017 Sportsman 850 setups, use this sequence: right rear (if separate), left front, right front. If your model differs because of ABS routing, follow the sequence in your service manual.

Single-person (pressure or syringe) method

  1. Attach the clear tubing to the bleed nipple and place the other end in the catch bottle containing a bit of fresh brake fluid.
  2. With the bleed nipple closed, have a helper pump the brake lever/pedal several times and hold pressure (or use a pressure bleeder or syringe on the master cylinder to pressurize). If using a pressure bleeder, set to a low-pressure setting per tool instructions.
  3. Open the bleed nipple slightly to allow fluid and air to exit into the tubing. Close the nipple before the helper releases the lever/pedal. Repeat until no air bubbles appear in the tubing and fluid runs clear.
  4. Keep the reservoir topped during the process to prevent air re-entry.
  5. Move to the next caliper in the sequence and repeat.

Two-person manual pump method

  1. Person A pumps the lever/pedal several times and holds firm pressure.
  2. Person B opens the bleed nipple to allow fluid to flow into the tubing and then closes it before Person A releases pressure.
  3. Repeat until clear fluid with no bubbles flows from each bleed nipple.
  4. Maintain fluid level in the reservoir at all times.

Flushing the system

After bleeding each caliper one pass, perform a final system flush by repeatedly drawing old reservoir fluid out with a syringe and replacing with fresh fluid, then repeating the bleed sequence until the fluid at each caliper and the reservoir is new and free of bubbles.

Final checks & torque

  • Torque bleed nipples and any removed caliper bolts to Polaris specifications from the service manual.
  • Clean residual fluid from all painted surfaces immediately with brake cleaner & a rag; brake fluid will damage paint and plastics.
  • Check pedal/lever firmness — it should be firm with no sponginess. If spongy, repeat bleeding until firm.
  • Inspect hoses, fittings, pads & rotors for wear or contamination; replace parts as needed.
  • Dispose of old brake fluid according to local hazardous waste rules.

Troubleshooting

  • Still spongy after multiple bleeds: suspect an internal ABS air trap or a soft hose; inspect lines and consider professional ABS bench bleeding if your unit has an integrated ABS module.
  • Persistent leaks: tighten fittings to spec and replace any damaged bleeder screws or hose fittings.
  • Contaminated or dark fluid immediately after servicing: perform another full flush and inspect reservoir cap/dust boot for contamination sources.

Maintenance tips

  • Record the service date and fluid type in your maintenance log. Schedule the next replacement in ~24 months or sooner if you ride in wet/humid conditions.
  • Carry a small DOT 4 bottle on long rides for emergency top-ups, but only use it to restore safe level until you can perform a full service.
  • Use new crush washers or sealing washers on bleeder fittings if your model uses them; reusing old washers can lead to leaks.

Following this MotoSport guide will keep your 2017 Polaris Sportsman 850 braking system performing safely and reliably. If you encounter ABS-specific issues or persistent air in the system, consult a qualified technician or authorized Polaris service center.

Related Shopping Categories

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Shop Brake Tools for a 2017 Polaris Sportsman 850 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.