How to Change the Coolant in a 2020 Suzuki DRZ400SM

Shop parts for a 2020 Suzuki DRZ400SM Dirt Bike.

Regular coolant changes are crucial for your 2020 Suzuki DRZ400SM. Cooling system maintenance ensures optimal performance and helps prevent engine overheating, especially for a model designed for both dirt – and street – riding. Below, find a step-by-step DRZ400SM-specific process you can follow right from your garage.

What You'll Need

  • Metric socket set (primarily 8mm, 10mm, and 12mm)
  • Phillips screwdriver
  • Caught-fluid pan for old coolant
  • Pre-mixed motorcycle coolant (silicate-free, phosphate-free, 50/50 blend recommended)
  • Distilled water (for flushing, optional but preferred)
  • Rags or shop towels
  • Protective gloves

Step 1: Prepare the Bike

  • Ensure the engine is completely cool before starting. Removing coolant from a hot engine is dangerous and can cause burns.
  • Stand the DRZ400SM upright or on a lift for easy access to the radiator and water pump.

Step 2: Remove Side Cover – Access the Water Pump

  • Use a 12mm socket to remove the left side cover for better access.

Step 3: Drain the Old Coolant

  • Locate the drain bolt at the bottom of the water pump cover – use a 10mm socket to loosen and remove it over your pan.
  • Remove the radiator cap (secured with a small screw on some models)–this allows coolant to drain more freely*.
  • Let all coolant flow out. Be sure to dispose of the old coolant according to local regulations.

Step 4: Flush the System (Recommended)

  • This step helps remove any remaining debris or old coolant.
  • Replace the drain bolt temporarily. Slowly fill the radiator with distilled water.
  • Remove the drain bolt, allowing the flush water to exit.
  • Repeat once if the system is especially dirty.

Step 5: Reinstall the Drain Bolt

  • Torque the drain bolt to factory spec (do not overtighten to avoid stripping the threads).

Step 6: Fill with New Coolant and Bleed Air

  • Fill the right radiator slowly with your selected pre-mixed coolant.
  • On some DRZ400SMs you will see a bleed screw on the water neck at the top front of the engine head. Loosen this a few turns (do not remove fully) to let trapped air escape—if your motor does not have this screw, skip to the next step.*
  • Continue filling until coolant exits the bleed screw, then snug it closed. Top up the radiator again as needed.
  • Open the bleed screw on the top of the left radiator (if equipped). As coolant exits, close it snugly.
  • With the radiator filled, tip the bike gently left and right to help remaining air bubbles rise out.
  • Top off the radiator one last time, ensuring it's fully filled to the neck, and replace the radiator cap.

Step 7: Run the Engine & Final Top-Off

  • Start the motorcycle and let it idle until it reaches normal operating temperature. This cycles the coolant and can dislodge any lingering air.
  • Turn off the bike and let it cool completely. Remove the radiator cap and top off as necessary.
  • Add about an inch of coolant to the overflow bottle, which helps maintain correct levels as the system heats and cools.*

DRZ400SM Model-Specific Notes

  • The DRZ400SM's high-revving, high-compression engine can run hot, especially in slow-moving traffic or on the trail. Do not skip routine coolant checks during warm weather riding.
  • Not all DRZ400SMs come with a water neck bleeder screw; check your model year’s hardware to know if you'll need this air-bleeding step.
  • Only use coolant compatible with your DRZ's aluminum radiator–avoid those containing silicates or phosphates, which can damage internal passages.
  • Check for leaks after each coolant service. Inspect all hose clamps, the radiator cap seal, and water pump for drips.

Troubleshooting

  • If you notice rapid coolant loss or overheating, address leaks or trapped air immediately.
  • Sludge or discoloration in old coolant is a sign of overdue maintenance–flush your system more thoroughly if you see these.

Maintaining the DRZ400SM’s cooling system will keep your ride safe, efficient, and ready for all terrain. Let MotoSport supply you with everything you need for your next maintenance interval.

*Steps confirmed and tested on DRZ400SM models – steps may differ for previous model years or race-prepped versions.

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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.