How to Change the Coolant in a 2018 Suzuki DRZ400SM

Shop parts for a 2018 Suzuki DRZ400SM Dirt Bike.

Keeping your 2018 Suzuki DRZ400SM’s coolant fresh is essential for reliable performance and smart long-term maintenance. Suzuki’s liquid-cooled thumper can tackle hot trail days or city commutes, but old or contaminated coolant can lead to overheating and internal damage. Here’s a proprietary MotoSport guide to changing your coolant – and a few owner notes about this legendary supermoto.

Tools and Materials Needed

  • Phillips screwdrivers (small and medium)
  • Socket wrench set (12 mm and 10 mm recommended)
  • Catch pan or a suitable container for old coolant
  • Pre-diluted 50/50 motorcycle coolant (avoid automotive coolant with silicates or phosphates)
  • Clean shop towels
  • Distilled water (if performing a flush)
  • Protective gloves & eye protection

Preparation – Safety First

  • Let the bike cool completely. Never remove the radiator cap on a hot engine due to pressure and burn risk.
  • Prop the bike up on a secure kickstand or stand.
  • Remove any aftermarket guards blocking radiator or water pump access.

Step-by-Step Coolant Change Procedure

  1. Remove Side Cover: Use a 12 mm socket to remove the right side cover. On the DRZ400SM, this improves access to the water pump and drain bolt.
  2. Open Radiator Cap: Carefully twist off the radiator cap. This helps coolant drain smoothly.
  3. Locate and Remove Drain Bolt: Find the water pump’s 10 mm drain bolt (bottom right side of the engine case, near the hose connection). Place your catch pan underneath. Remove the bolt and allow coolant to drain completely.
  4. Optional – Flush with Distilled Water: Reinstall the drain bolt. Fill the radiator with distilled water, replace the radiator cap, and briefly run the engine (1–2 minutes) to circulate. Shut off, cool down, remove the cap, and drain again by removing the bolt. This removes more debris or old coolant.
  5. Reinstall Drain Bolt: Use a new crush washer if necessary. Tighten the drain bolt to specification (consult your service manual for exact torque).
  6. Fill with New Coolant: Slowly add pre-mixed 50/50 coolant into the radiator until full. Squeeze radiator hoses gently to help purge air pockets.
  7. Bleed the System: With cap off, start the engine and let it idle. Watch the coolant level – as the thermostat opens, you may see air bubbles come up. Top off as needed.
  8. Replace Radiator Cap and Side Cover: Once the level stabilizes, reinstall the radiator cap and side cover.
  9. Check Overflow Reservoir: Make sure it’s filled to the listed range on the tank (behind the rear brake pedal on this model). Top off if necessary.
  10. Test Ride and Inspect: After a short ride, check the coolant level and inspect for leaks around the drain bolt and hoses.

Special Notes for DRZ400SM Owners

  • The DRZ400SM uses a relatively small coolant capacity. Never exceed the max fill line to prevent overflow during hot operation.
  • This model is sensitive to air pockets in the cooling system – always bleed thoroughly to avoid overheating, especially after hard riding or supermoto track days.
  • Use only motorcycle-specific coolant; silicates in automotive products can damage the DRZ’s water pump seal and radiator internals.
  • If your SM has aftermarket radiators or a racing thermostat, verify coolant capacity and follow the manufacturer’s recommendations.

Disposal

  • Never pour used coolant down a drain or in the soil. Bring it to your local recycling center or hazardous waste facility.

Coolant changes are straightforward, but attention to air bleeds and using correct products are especially important on the DRZ400SM. Stay on top of routine maintenance for fun, worry-free riding.

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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.