How to Change the Coolant in a 1999 Yamaha XT350
Shop parts for a 1999 Yamaha XT350 Dirt Bike.
Routine coolant changes are essential for the longevity and performance of your 1999 Yamaha XT350. This air and liquid-cooled dual-sport is known for its reliability, but good cooling system maintenance is still key to keeping it running at its best–especially during demanding off-road rides and in hot weather. Follow this comprehensive MotoSport-exclusive guide to safely and effectively replace the coolant on your XT350.
Preparation – What You Need
- Fresh motorcycle coolant (consult XT350 manual for type and capacity)
- Drain pan
- 10mm socket or wrench
- New sealing washer for drain bolt
- Funnel
- Gloves and shop rags
- Distilled water (for flushing, if needed)
Step-by-Step Guide
- Cool the Engine: Ensure your XT350 is cold before starting to prevent burns from hot coolant.
- Locate the Radiator Cap & Drain Plug:
- The radiator fill cap is usually atop the radiator.
- The coolant drain bolt on the XT350 is a 10mm bolt found at the lowest point of the steel pipe from the cylinder block to the water pump. It has a sealing washer under the bolt head–save or replace the washer as needed.
- Remove the Radiator Cap: Slowly open the cap to release any built-up pressure.
- Drain the System: Position a pan and remove the 10mm drain bolt. Allow coolant to fully drain. Dispose of old coolant properly.
- Flush (Optional but Recommended): If the coolant is old, rusty, or unknown, fill the system with distilled water. Replace the drain bolt and run the engine briefly. Drain again. Repeat until the draining water runs clear.
- Reinstall the Drain Bolt: Fit a new sealing washer if possible. Torque the bolt snugly, but do not overtighten.
- Add New Coolant: Using a funnel, slowly add fresh, pre-mixed coolant into the radiator until full. Squeeze radiator hoses gently to help purge trapped air. Fill the reservoir tank up to the upper level mark.
- Bleed Air from the System: Loosen the pump purge (bleeder) bolt until air and bubbles stop, then retighten. This helps ensure a fully filled system for the XT350, which uses a combined air-and-liquid cooling system.
- Heat Cycle the Engine: Start the bike and let it idle until it's up to normal temperature. Briefly rev up to 4,000–5,000 rpm a few times to help evacuate air pockets. Shut off and let it cool completely.
- Recheck and Top Off: Once cool, open the radiator cap and top off as needed. Check the reservoir and fill to the full line if necessary.
MotoSport Tips for XT350 Owners
- The XT350 features both air and liquid cooling, making a clean cooling channel critical for temperature control when navigating slow, technical terrain or hot environments.
- The water pump's 10mm drain bolt and its sealing washer are model-specific; always check for leaks after reinstallation and replace the washer to ensure a solid seal.
- Frequently inspect coolant level in the reservoir after your first few rides post-change, as air bubbles might work themselves out after the initial refill–topping off may be necessary.
Important Reminders
- Never work on the cooling system when hot–wait until the bike is fully cool.
- Dispose of used coolant responsibly; it is toxic to humans, pets, and the environment.
- Use only recommended, motorcycle-specific coolant for Yamaha models; automotive formulas may lack the correct corrosion-inhibiting additives for mixed-metal engines.
Regular coolant maintenance on your Yamaha XT350 protects your investment and delivers the best possible performance & ride. Now that you know how, take care of your machine and enjoy the trails.
Related Shopping Categories
Shop Radiators for a 1999 Yamaha XT350 Dirt Bike.
Shop Coolant for a 1999 Yamaha XT350 Dirt Bike.
Shop Temperature Sensors for a 1999 Yamaha XT350 Dirt Bike.
Shop Tools for a 1999 Yamaha XT350 Dirt Bike.
Shop Radiator Hoses for a 1999 Yamaha XT350 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.