How to Change the Coolant in a 2016 KTM 150SX

Shop parts for a 2016 KTM 150SX Dirt Bike.

Keeping your 2016 KTM 150SX running at peak performance means routine maintenance, and a coolant change is a critical step in that process. This proprietary MotoSport guide walks you through the correct coolant flush and refill procedure, along with key model-specific tips for your 150SX.

Why Coolant Matters for Your KTM 150SX

The KTM 150SX's high-performance two-stroke engine creates significant heat under heavy riding conditions. Fresh coolant maintains optimal engine temperature, maximizes performance, and protects internal engine components from corrosion and overheating. It is recommended to change the coolant after approximately every 40-50 hours of ride time or if you notice the coolant is dirty or contaminated.

What You Will Need

  • Fresh coolant (use a high-quality motorcycle-specific coolant compatible with aluminum radiators)
  • 10mm wrench or socket
  • Drain pan
  • Funnel
  • Protective gloves – coolant can be harmful to skin
  • Clean rags or paper towels

Step-by-Step Guide: Coolant Change Process

  1. Ensure the engine is cool.
    Never open the radiator cap when the engine is hot, as pressurized steam or hot coolant can cause burns.
  2. Remove the radiator cover.
    For all 125/150 models, remove the radiator shroud to access the cap and drain bolt. Use the 10mm wrench to remove bolts if necessary.
    (Reference: Section 15.4, Owner's Manual)
  3. Position your drain pan.
    Locate the water pump drain bolt on the lower right side of the engine. Position the drain pan directly under the bolt.
  4. Remove the radiator cap.
    This allows air into the system so coolant drains freely.
  5. Remove the coolant drain bolt.
    Carefully loosen and remove the bolt. Coolant will begin to flow; let it drain completely.
    Tip: Slightly lean the bike side-to-side to help any trapped coolant exit the system.
  6. Inspect the old coolant for contamination.
    If the coolant is discolored, rusty, or has debris, check for signs of gasket failure or corrosion inside the cooling system.
  7. Reinstall the drain bolt.
    Once the coolant has stopped draining, reinstall the drain bolt securely, ensuring no debris is present on the sealing surface.
  8. Refill with new coolant.
    Insert a funnel into the radiator fill neck. Pour coolant until it reaches the bottom of the fill neck. Avoid overfilling. The 2016 150SX typically takes just under 1 liter, but always check actual fill visually.
    Do not mix coolant types; always use the same formulation to prevent reactions.
  9. Bleed the cooling system.
    With the cap off, gently tilt the bike left and right again to release trapped air bubbles. Squeeze the radiator hoses by hand to help purge air.
    Fill as needed if the coolant level drops after air escapes.
  10. Reinstall the radiator cap and covers.
    Confirm the cap is securely in place and reattach the radiator shrouds.
  11. Start and check for leaks.
    Start the engine and let it idle with the bike upright. Watch the coolant level after a minute-if it drops, top off as needed. Check around the drain bolt and hoses for leaks.

Special Considerations for the 2016 KTM 150SX

  • The 2016 model uses an aluminum radiator–avoid coolant containing silicates or automotive anti-freezes, as these can cause internal corrosion.
  • Always dispose of old coolant responsibly–it is toxic to pets and the environment.
  • The plastic radiator covers are an integral part of the shroud; handle them gently to avoid cracking during removal and reinstallation.
  • Check the system for leaks after your first ride; re-torque the drain bolt if needed.
  • If riding in extreme cold, ensure your coolant provides adequate freeze protection. 

When to Inspect the Cooling System Further

  • If you notice recurring low coolant, visible leaks, or overheating, inspect radiator hoses, seals, and the water pump for wear or damage.
  • Replace seals or the radiator cap if they show signs of old age or leakage.

Coolant changes on your KTM 150SX are straightforward and provide significant engine protection. For OEM and performance cooling parts, shop parts for a 2016 KTM 150SX Dirt Bike.

Related Shopping Categories

Shop Radiators for a 2016 KTM 150SX Dirt Bike.

Shop Coolant for a 2016 KTM 150SX Dirt Bike.

Shop Temperature Sensors for a 2016 KTM 150SX Dirt Bike.

Shop Tools for a 2016 KTM 150SX Dirt Bike.

Shop Radiator Hoses for a 2016 KTM 150SX Dirt Bike.

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.