How to Change the Coolant in a 2018 Suzuki DRZ400S

Shop parts for a 2018 Suzuki DRZ400S Dirt Bike.

Keeping the coolant fresh and at the proper level is vital to the long-term reliability of your 2018 Suzuki DRZ400S–especially if you ride in demanding off-road conditions. This guide, crafted exclusively for MotoSport.com riders, provides detailed instructions and important tips specific to the DRZ400S, ensuring a smooth, hassle-free coolant change experience.

What You Need

  • Pre-mixed, motorcycle-safe coolant (50/50 blend recommended)
  • 12mm socket and wrench set
  • Phillips screwdriver (small and medium)
  • Drain pan
  • Shop rags
  • Protective gloves

Before You Begin

  • Only service the cooling system when the engine is completely cool to avoid burns.
  • The 2018 DRZ400S does not use a thermostat and, depending on production run, may or may not have a dedicated air bleeder on the water neck. If the water neck points straight up, your model will not have the bleeder there; you will still have one on the left radiator.
  • Note that the OEM coolant should be regularly replaced for optimal cooling and anti-corrosion protection.

Step-by-Step: Coolant Change Procedure

  1. Remove Side Fairing:
    • Unscrew and remove the right-side plastic fairing using the 12mm socket. This will give access to the water pump drain bolt.
  2. Radiator Cap Removal:
    • Remove the small screw securing the radiator cap (if installed). Take off the cap. This allows air to enter so coolant drains freely.
  3. Drain the Old Coolant:
    • Place a drain pan under the water pump. Locate and remove the drain bolt on the water pump cover (10mm or 12mm hex head, under the right side by the lower radiator hose).
    • Allow all coolant to drain completely. If your bike is on a stand, gently rock it side to side to help evacuate any trapped coolant.
  4. Optional: Flush the System
    • If switching coolant types or it's been a long time between changes, consider flushing with distilled water (never use tap water). Pour in distilled water, replace the drain bolt, run the motor for 30 seconds, then drain again. Repeat until water runs clear.
  5. Reinstall the Drain Bolt:
    • Clean the drain bolt threads and surrounding area. Reinstall the bolt securely, but do not overtighten.
  6. Purge Air from the System:
    • Your DRZ400S may have a bleeder screw at the top front of the cylinder head (water neck) and another on top of the left radiator. Open these a few turns; do not remove fully.
    • Slowly pour fresh coolant into the right radiator until liquid begins to exit the bleeder screws. Tighten the screws as soon as coolant flows steadily from each location.
    • If your model only has the left radiator bleeder screw, keep an eye on that alone.
  7. Top Off Coolant:
    • Continue filling the radiator up to the neck as air escapes. Rock the bike gently left and right to dislodge any trapped air. Re-check fluid level and top off as needed.
  8. Reinstall Radiator Cap – Run Engine:
    • Replace the radiator cap. Start the engine and let it idle until up to operating temperature (idle only, do not rev hard). Shut off and let it cool.
    • Once cooled, carefully remove the radiator cap again and top off coolant if level has dropped.
  9. Check Overflow Reservoir:
    • Add or adjust coolant in the overflow tank to ensure about 1 inch of fluid is present. This is extra insurance against overheating under tough riding conditions.
  10. Reinstall Fairing – Final Inspection:
    • Replace the side fairing. Start and warm up the engine again. Inspect for leaks and verify proper coolant level one final time after a ride.

DRZ400S Owner Tips & Notes

  • The DRZ400S is known for its ruggedness, but the cooling system can become vulnerable if air pockets remain after coolant changes–always purge thoroughly.
  • If you do a lot of slow, technical riding or ride in hot climates, consider coolant additives formulated for higher-performance heat transfer.
  • Always dispose of old coolant safely according to your local environmental regulations.

Keeps your 2018 Suzuki DRZ400S running cool and worry-free–make coolant maintenance a regular part of your riding routine.

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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.