How to Change the Coolant in a 2015 Suzuki DRZ400S: Step-by-Step Guide

Shop parts for a 2015 Suzuki DRZ400S Dirt Bike.

Maintaining the cooling system on your 2015 Suzuki DRZ400S is essential for performance and long engine life. Coolant not only manages engine temperature but also protects vital cooling system components from corrosion and damage. Follow this proprietary MotoSport guide to expertly change the coolant on your DRZ400S and keep your bike running cool in every condition.

Tools & Supplies Needed

  • Socket wrench set (including a 10mm socket and a 12mm socket)
  • Small and medium Phillips screwdriver
  • Drain pan
  • Pre-diluted motorcycle coolant (50/50, suitable for aluminum radiators)
  • Clean rags
  • Optional: compressed air (if flushing)
  • Gloves and safety glasses

Important Note for DRZ400S Owners

Your DRZ400S features a robust, dual-radiator system designed for tough dual-sport use. Some DRZ400 models have an air bleed screw at the water neck and another at the left radiator, but not all versions do—double-check your bike's configuration as this can speed up air removal in the system. Also, the DRZ400S does NOT use a thermostat, unlike some street bikes. Always use a bike-safe, silicate-free coolant to protect engine internals and radiator from corrosion.

Step 1: Remove Side Cover and Access the Drain Bolt

  • Park the bike securely on level ground and ensure the engine is cold.
  • On the right side of your DRZ400S, use a 12mm socket to remove the side panel. This provides access to the water pump area and drain bolt.

Step 2: Remove the Radiator Cap

  • Locate the radiator cap on the right radiator. Remove the small screw securing the cap, if present.
  • Carefully remove the radiator cap to release system pressure. (Use a rag to protect your hand in case any residual pressure remains.)

Step 3: Drain the Old Coolant

  • Place your drain pan below the water pump cover. Remove the coolant drain bolt (10mm socket) and allow all coolant to fully drain.
  • You may open the air bleed screws on the water neck and left radiator if equipped; this will allow coolant to drain quicker and help remove trapped air.

Step 4: Optional – Flush the System

  • If changing coolant types or if the old coolant appears contaminated, flush the system with distilled water.
  • Reinstall the drain bolt and fill the radiators with distilled water, then repeat the draining process. For full flushing, remove lower radiator hoses and use low-pressure compressed air to clear the system. Never use tap water—always use distilled to avoid mineral buildup.

Step 5: Reinstall Drain Bolt and Prepare to Fill

  • Reinstall and torque the coolant drain bolt. Avoid over-tightening to protect the aluminum threads.
  • Ensure all bleed screws and hose connections are secure before filling.

Step 6: Fill with Fresh Coolant and Bleed Air

  • Slowly begin filling the right radiator with pre-mixed coolant.
  • Open air bleed screws (if available). As coolant flows, allow air to escape from the water neck and left radiator. Once coolant begins to dribble out the bleed screws without air, snug them down gently.
  • Continue to top-off the right radiator. Gently rock the bike side-to-side to help trapped air bubbles rise to the fill neck, then top-off again.

Step 7: Final Reassembly and Top-Off

  • Replace the radiator cap and reinstall the side cover.
  • Start the bike and let it idle for several minutes, monitoring temperature and looking for leaks. Shut down and let it fully cool.
  • Remove the radiator cap and check coolant level, topping off as needed.
  • Add a little coolant to the overflow reservoir (approximately 1 inch). This helps monitor levels and prevents air from entering after hard riding.

Model-Specific Tips for the 2015 DRZ400S

  • Do not use car coolants or water alone, as these can damage the magnesium water pump case and radiators.
  • No need to remove both radiators or disassemble major components—the procedure above is streamlined for easy home maintenance.
  • If your DRZ400S runs hotter than normal after service, double-check for trapped air: re-bleed using the steps above.
  • Follow coolant change intervals: The DRZ400S should have its coolant changed at least every two years or sooner if you ride in harsh environments.

Changing the coolant in your 2015 Suzuki DRZ400S is simple, quick, and a critical part of bike care. Maintain your Suzuki for maximum performance with regular coolant service, and shop parts for a 2015 Suzuki DRZ400S Dirt Bike.

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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.