To change motorcycle coolant, let the engine cool completely, drain the old coolant from the drain bolt on the water pump or radiator, flush if your manual calls for it, refill with the correct coolant mix, remove trapped air, and recheck the level. The job is straightforward on most liquid-cooled bikes, but the coolant type, capacity, bleed procedure and torque values come from your service manual, so have it open before you start.
This guide gives the steps, the tools and the points where a torque wrench or a professional is the right call.
When should you change motorcycle coolant?
Coolant breaks down over time. Its corrosion inhibitors wear out, and old coolant can leave deposits or eat at aluminum parts. Many manufacturers set an interval in years, and some use mileage too. Typical intervals run from about two to five years depending on the coolant and the maker. Your owner's manual or service manual gives the real number for your bike.
Change it sooner if the coolant looks rusty, oily or cloudy, or if you have just repaired a leak or replaced a hose, water pump or radiator. See our maintenance schedule for how this fits with other jobs. If you are choosing a coolant, read what coolant your motorcycle needs.
Tools and parts
- Coolant of the type and spec in your manual (pre-mixed, or concentrate plus distilled water)
- Drain pan sized for the full system
- New crush washers or sealing washers for any drain bolt
- Funnel, ideally a long-neck type
- Wrenches or sockets for the drain bolt and any fairing fasteners
- Torque wrench (needed for drain bolts and covers)
- Distilled water for flushing, if your manual allows it
- Rags, gloves and eye protection
- Service manual for capacity, bleed procedure and torque values
- A stand to keep the bike upright and level
What the manual must tell you
| Item | Why it matters |
|---|---|
| Coolant type and mix ratio | Wrong coolant can damage aluminum and seals |
| System capacity | Bikes vary widely, so never guess |
| Drain bolt locations | Some bikes have more than one |
| Bleed procedure | Many engines trap air if filled the wrong way |
| Torque values | Drain bolts and covers are in aluminum |
Safety first
- Never open a hot radiator cap. The system is under pressure and the coolant can scald. Wait until the engine is fully cool.
- Coolant is toxic. Keep it away from pets and children, and wipe up spills at once.
- Keep coolant off brake rotors, pads and tires.
- Wear eye protection when opening a pressurized system.
How to change motorcycle coolant: step by step
1. Cool the engine and level the bike
Park the bike on a level surface and let it cool for several hours if it has been ridden. Put it upright on a stand if you have one, since a bike tilted on its side stand will not drain or fill evenly.
2. Remove panels
Take off the seat, tank cover or fairing panels as needed to reach the radiator cap, the reservoir and the drain bolt. Keep fasteners in order and note their lengths so they go back in the right holes.
3. Open the radiator cap
Press down and turn the cap slowly to the first stop to release any residual pressure. Then remove it. On some bikes the radiator cap sits under a cover or on the engine side. Follow your manual.
4. Position the pan and open the drain
Place the pan under the drain bolt, which is usually on the water pump housing or the bottom of the radiator. Remove the bolt and let the coolant drain fully. Remove the reservoir cap too if you can, to let air in.
5. Empty the overflow reservoir
The overflow tank holds extra coolant. Take it off or siphon it out, rinse it, and put it back. Some bikes need a hose disconnected to empty it.
6. Inspect the old coolant
Look at the old fluid. Rusty brown, sludgy, oily or milky coolant points to an issue. Oil in the coolant or coolant in the oil can mean a failed head gasket, water pump seal or oil cooler. Stop and have it diagnosed. Our motorcycle overheating guide lists other causes of cooling trouble.
7. Flush if recommended
If the old coolant was dirty, and your manual allows it, close the drain and fill the system with distilled water, run the engine briefly to circulate it, let it cool, and drain again. Repeat until the water runs clear. Some water stays in the engine after flushing, so it dilutes the new coolant a little; your manual may say how to allow for that. Do not use a chemical cleaner unless the manual approves it.
8. Refit the drain bolt with a new washer (torque wrench step)
Use a new washer and tighten the bolt to the value in your service manual. These bolts thread into aluminum and are easy to strip, so use the torque wrench.
9. Fill with new coolant
Use the funnel and add coolant slowly through the radiator filler, giving air time to escape. Tilt the bike gently side to side or upright as your manual says to help release bubbles. Fill until the coolant reaches the base of the filler neck, then fill the reservoir to the line your manual shows.
10. Bleed the air
This step matters most. With the cap off or the manual's bleed procedure followed, start the engine and let it idle. Watch the level in the filler neck. It will drop as air escapes and the thermostat opens. Top up as needed. Some bikes have a bleed screw on the radiator or a hose to open. Others call for revving or squeezing a hose. Follow your manual.
Keep going until the level stops dropping, the fan cycles on and off and no bubbles rise. Then refit the cap.
11. Check the level when cold
After the bike cools, recheck the reservoir. The Motorcycle Safety Foundation's T-CLOCS checklist includes checking coolant level as part of the Oil and Other Fluids step and checking hoses and fittings for leaks. Top up as needed to the marks on the reservoir.
12. Test ride and recheck
Take a short, gentle ride. Watch the temperature gauge or light. Let the engine cool again, then recheck the level and look for drips around the drain bolt, hoses and water pump.
How to dispose of used coolant
Do not pour it down a storm drain or onto the ground. Put it in a sealed, labeled container and take it to a recycling or hazardous waste drop-off. Many auto parts stores and shops accept it, and some local waste programs run collection days. Call ahead, since rules vary by location.
How much does a motorcycle coolant change cost?
A DIY change costs the coolant, a washer and some supplies, and varies by bike and brand. A shop charges labor on top, and bikes with a lot of fairings or a hard-to-bleed system can cost more. Prices vary by bike, region and shop. The repair cost guide gives context for typical shop prices.
Common mistakes
- Opening the radiator cap on a hot engine
- Using the wrong coolant or an incorrect mix
- Leaving air trapped in the system
- Overtightening the drain bolt in the aluminum casing
- Forgetting to empty and refill the overflow tank
- Not checking the level again after the first ride
When to see a mechanic
Book a shop visit if:
- The old coolant is oily, milky or full of metal flakes
- The engine overheats after the change, or the temperature climbs when idling
- You cannot get the air out or the level keeps dropping
- Coolant is leaking from the water pump, a hose or the radiator
- You see white smoke from the exhaust or coolant in the oil
- You do not have the manual's coolant spec, capacity or torque values
If the temperature warning comes on while riding, pull over and shut the engine off. Continuing can warp the head or damage the engine. For routine service, our maintenance services page lists shops that handle cooling work, and you can compare motorcycle repair shops in Phoenix or another city near you.
Quick checklist
- Cool engine, level bike, manual open.
- Drain with a new washer, torque the bolt to spec.
- Fill with the right coolant and bleed the air.
- Recheck the level cold after a short ride.
- Recycle the old coolant.
Frequently asked questions
Can I use car antifreeze in my motorcycle?
Only if it meets the specification in your manual. Many bikes call for a silicate-free, aluminum-safe coolant, so read the label and match your manual rather than going by color.
Should I use pre-mixed coolant or concentrate?
Pre-mixed is simplest because the ratio is already correct. If you use concentrate, mix it with distilled water to the ratio your manual or the coolant label gives.
How do I know if there is air in the cooling system?
Signs include the temperature gauge climbing, gurgling sounds, a cold-running hose while the engine is hot, or the fan running more than usual. Air pockets cause hot spots, so bleed the system and recheck the level.
Is old coolant dangerous?
Used coolant is toxic and can taste sweet to pets, so keep it away from animals and children and recycle it. Do not pour it on the ground or down a drain.