How to Bleed & Replace Brake Fluid on a 1998 Polaris Sportsman 500 4X4

Shop parts for a 1998 Polaris SPORTS500 ATV.

This MotoSport-exclusive guide walks you through flushing old brake fluid and bleeding the brake system on a 1998 Polaris Sportsman 500 4X4. Follow these steps carefully to restore firm braking and remove moisture/contamination from the system. Read each section fully before starting and work methodically.

Notes specific to the 1998 Polaris Sportsman 500 4X4

  • The Sportsman 500 uses separate front and rear master cylinders: a handlebar master cylinder for the front brakes and a foot-pedal/master-cylinder assembly for the rear. Treat each circuit independently.
  • This model does not use ABS; bleeding procedures are standard hydraulic bleeding rather than ABS-specific cycles.
  • Brake line routing and caliper access are compact on this ATV. You may need to remove wheels or skid plates to reach calipers and bleed nipples easily.
  • Always inspect rubber hoses, banjo bolts, copper crush washers, and caliper boots while the system is open. On a late-90s Sportsman, aging hoses and worn crush washers are common service items.
  • When in doubt on fluid type, check the reservoir cap labeling and the owner's manual. Polaris Sportsman typically uses DOT-rated brake fluid; use a DOT 3 or DOT 4 fluid that meets OEM specs and never mix mineral-oil type systems with DOT fluid.

Tools & supplies

  • Correct DOT brake fluid (fresh, unopened bottle)
  • Brake bleeder kit or clear tubing and a catch bottle
  • Wrenches for bleed nipples (usually 8mm or 10mm)
  • Clean rags, gloves, safety glasses
  • Turkey baster or syringe to remove old fluid from reservoirs
  • Jack or ramps and stands if wheel removal is required
  • Torque wrench for caliper/banjo bolts and reservoir cap
  • Small funnel or bleed reservoir funnel

Preparation

  • Work on a level surface, park the ATV in gear and block wheels to prevent movement.
  • Wear eye protection and gloves. Brake fluid damages paint & plasticscover bodywork where needed.
  • Refer to the vehicle service manual for torque values and any model-specific cautions.
  • Identify the front and rear reservoirs. Remove any debris around caps before opening to avoid contamination.

Step 1 Remove old fluid from the reservoir

  • Open the reservoir cap(s) for the circuit you are servicing (front and/or rear). Do not let dirt fall in.
  • Use a turkey baster or syringe to suck out as much old fluid as possible until the reservoir is nearly empty.
  • Refill with fresh DOT fluid up to the "MAX" mark. Do one circuit at a time to avoid crossing systems.

Step 2 Determine bleed sequence

  • For each master cylinder, start bleeding at the caliper farthest from that master and finish with the closest. Typical sequence on this Sportsman: rear circuit left rear then right rear if the master is centrally located on the pedal assembly; front circuit (handlebar master) farthest front caliper first, then the other front caliper.
  • If you find a single combined hydraulic circuit, still follow farthest-to-closest logic. If you're unsure, identify line runs visually to determine which caliper is farthest.

Step 3 Bleeding procedure (manual or vacuum)

  • Place a clear hose on the bleed nipple and route the other end into a bottle partially filled with fresh fluid to prevent air ingestion.
  • Crack the bleed nipple about 1/4 to 1/2 turn. Keep the reservoir topped up during the entire procedure.
  • Have an assistant slowly depress the lever (for front) or press the pedal (for rear) several times, then hold pressure. While held, open the nipple to let fluid/air out, then close the nipple before the lever/pedal is released. Repeat until fluid runs clear and bubble-free.
  • Alternatively, use a vacuum bleeder on the caliper bleed nipple and pump until no air bubbles appear in the hose and reservoir level stabilizes.
  • Work methodically: bleed until no bubbles, then move to the next caliper per your sequence. Always top up the reservoir so it never runs dry introducing air there will prolong the job.

Step 4 Final flushing (optional but recommended)

  • To fully replace old fluid, continue bleeding each caliper until the fluid coming out matches the new fluid color and clarity. This may require multiple reservoir refills.
  • When finished, tighten bleed nipples to spec hand-tight plus a small turn (consult manual), wipe off any spilled fluid, and reinstall caps with clean seals.

Step 5 Inspect & torque

  • Check banjo bolts and crush washers at calipers for leaks. Replace crush washers if removed or if they appear flattened/damaged.
  • Tighten any caliper or brake-line fittings to the manufacturer's torque spec. If you don't have the spec on hand, tighten to a firm, secure feel and re-check for leaks.

Step 6 Bed-in & test

  • With the ATV still supported and wheels installed, apply the lever/pedal several times to confirm a firm, consistent feel and that the lever doesn't pull to the bar or floor with continued pressure.
  • Do a slow, low-speed brake test in a safe area to verify braking function and listen for abnormal noises.
  • Inspect around calipers, lines, and master cylinder for leaks after the test ride and after several uses.

Common issues & model-specific reminders

  • Sticky caliper pistons and leaking seals are common on older Sportsman models. If you see fluid near boots or uneven pad wear, remove calipers and service pistons/pads.
  • If the brake pedal or lever remains spongy after thorough bleeding, investigate hose expansion (old rubber hoses), internal master cylinder wear, or contaminated caliper internals. These components may need replacement.
  • Replace copper crush washers on banjo bolts anytime you open them to ensure a leak-free seal.
  • Keep brake fluid away from painted surfaces & plastics; it will damage decals and trim. Clean spills immediately with water.

Maintenance intervals & recommendations

  • For off-road ATVs, MotoSport recommends flushing brake fluid at least every 1-2 years or sooner if you notice degraded pedal feel, water-contaminated fluid, or corrosive storage conditions.
  • Inspect brake hoses and fittings annually; replace aged hoses on the Sportsman 500 as preventive maintenance.

Disposal

  • Used brake fluid is hazardous waste. Collect and dispose of it at a local hazardous waste facility or follow municipal disposal rules.

Following this MotoSport guide will get your 1998 Polaris Sportsman 500 4X4's brakes flushed and bled properly. If you encounter seized fittings, persistent leaks, or internal master/caliper failures, replace the faulty parts before returning the ATV to service.

Related Shopping Categories

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Shop Brake Tools for a 1998 Polaris SPORTS500 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.