How to Bleed and Replace Brake Fluid on a 2018 Polaris Sportsman Touring 850 SP
Shop parts for a 2018 Polaris Sportsman Touring 850 SP ATV.
This MotoSport-exclusive guide walks you through safely draining, flushing, and refilling the brake system on a 2018 Polaris Sportsman Touring 850 SP. Follow each step precisely, use quality parts and DOT 4 brake fluid, and perform the job on a flat, stable surface. If you're uncomfortable with hydraulic work, stop and have a qualified technician complete the service.
What you'll need
- DOT 4 brake fluid (new, unopened)
- Brake bleeder kit or clear tubing with a one-way valve
- Brake fluid collection container
- 10 mm and 8 mm wrenches (bleeder and reservoir fasteners)
- Turkey baster or fluid-siphon pump
- Clean rags and isopropyl alcohol for cleanup
- Gloves and eye protection
- Service manual or shop manual for torque specs and bleed sequence
Model-specific notes for the 2018 Sportsman Touring 850 SP
- The Sportsman 850 SP uses a hydraulic brake system with a master cylinder reservoir located under the front rack area; access requires removing the rack and reservoir cover on some trims. Keep the reservoir cap and diaphragm clean to avoid contamination.
- Polaris recommends DOT 4 fluid for this model. Do not mix DOT 3, DOT 4, and DOT 5 silicone fluid with DOT 4; mixing can damage seals and reduce braking performance.
- The rear brake line routing on the Touring model includes a split to the twin rear calipers on the towing-equipped models. Confirm which calipers are on your machine and follow the bleed sequence accordingly.
- If your machine has electronic brake components or brake sensors from aftermarket accessories, disconnect electrical power to avoid accidental activation while working.
- Inspect hoses, fittings, banjo bolts and caliper pistons for corrosion or leaks while you have the system open. Replace any degraded lines with OEM-spec parts available through MotoSport if needed.
Preparation
- Park the ATV level, engage parking brake, and remove the key. Work on cool brakes.
- Remove the front rack or reservoir access panel to expose the master cylinder reservoir. Clean the area around the cap to prevent dirt entry.
- Place rags around the reservoir and lay a drip tray under the ATV. Brake fluid will damage paint and plastics.
- Remove the cap and diaphragm; use a turkey baster or siphon to remove as much old fluid from the reservoir as possible. Dispose of fluid per local regulations.
- Refill the reservoir to the max line with fresh DOT 4 fluid, keeping the cap off but reseal ready to prevent contamination.
Recommended bleed sequence
Use the factory-recommended sequence where available. If you don't have the manual, a safe general sequence for Sportsman Touring is: farthest caliper from master cylinder first, then next farthest, finishing with the closest. Typically that means:
- Rear right caliper
- Rear left caliper
- Front right caliper
- Front left caliper
- Finally check master cylinder level and top as needed
Bleeding method (single-person pressure bleed)
- Attach clear tubing to the bleeder screw of the first caliper and place the other end in a container partially filled with fresh brake fluid to prevent air re-entry.
- Open the bleeder screw ~1/4 turn with the correct wrench. Do not fully remove it.
- Gently squeeze the brake lever/pedal repeatedly to push fluid and bubbles out. Keep an eye on the reservoir and top up frequently to avoid running dry.
- When the fluid runs clear and bubble-free, close the bleeder screw while pressure is applied (if possible) or immediately after the final squeeze to minimize air entry.
- Move to the next caliper and repeat until all calipers are clear. Monitor reservoir level throughout and maintain it between MIN and MAX.
- After completing the sequence, pump the brake lever/pedal to build firm pressure. If the lever feels spongy, repeat the bleeding process until lever firmness is restored.
Alternative method (two-person manual bleed)
- One person pumps the brake lever/pedal several times and holds it depressed.
- While held, the second person opens the bleeder screw to let fluid escape, then closes it before the lever/pedal is released. Repeat until no bubbles appear.
Bench checks & final steps
- Clean all fittings and torque bleeder screws to spec (refer to your manual for torque values). Wipe any spilled fluid immediately with isopropyl alcohol.
- Top the reservoir to the MAX mark, reinstall the diaphragm and cap, and secure the access panel or rack.
- Test brake lever/pedal feel with the ATV stationary. A firm feel indicates successful bleed. If soft, re-bleed.
- Perform a slow road test in a safe area to confirm braking performance and check for leaks. Recheck fluid level after the test and adjust as needed.
Inspection & parts notes specific to the 2018 Sportsman Touring 850 SP
- Banjo bolts use crush washers that should be replaced whenever removed. Reuse old washers can cause leaks; keep new washers on hand.
- OEM caliper hardware and brake line assemblies are available through MotoSport and are recommended for correct fit and corrosion resistance.
- If you encounter persistent air or a soft pedal after repeated bleeds, inspect the master cylinder for internal leakage or an aging seal. Master cylinder replacement may be necessary.
- Check wheel bearings, hubs and caliper slide pins for wear or corrosion while wheels are off. Binding or seized pins can mimic hydraulic problems.
Safety reminders
- Never reuse old fluid or top up with unknown fluid types. DOT 4 only.
- Brake fluid is hygroscopic; once opened, store properly and use within the manufacturer's recommended time frame.
- Avoid skin and paint contact with brake fluid. Rinse immediately with water if contact occurs and clean painted surfaces with a mild detergent.
Following this MotoSport guide will give you a clean, firm brake system on your 2018 Polaris Sportsman Touring 850 SP. If you need OEM replacement parts, hardware or brake fluid, see our parts selection linked above.
Related Shopping Categories
Shop Brake Fluid for a 2018 Polaris Sportsman Touring 850 SP ATV.
Shop Brake Bleeders for a 2018 Polaris Sportsman Touring 850 SP ATV.
Shop Brake Pads for a 2018 Polaris Sportsman Touring 850 SP ATV.
Shop Brake Lines for a 2018 Polaris Sportsman Touring 850 SP ATV.
Shop Brake Tools for a 2018 Polaris Sportsman Touring 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.