When to replace your motorcycle coolant? Can you do it yourself?

Liquid-cooled motorcycles have an extra system that air-cooled bikes don't have, and guess what? It requires maintenance. Over time and with use the coolant becomes more acidic and can begin to corrode and damage the insides of your engine and radiator and water pump. Coolant hoses also deteriorate over time and often crack internally or become soft and bulge, all signs that replacement is needed.

Coolant life varies with the type used and operating conditions. Engine coolant performance deteriorates over time. This can be caused by a build-up of aluminium corrosion or a change in the fluid to coolant ratio when periodically topped up. Most coolants contain special ingredients to help keep the solution alkaline. Over a period of time these lose their effectiveness, so the coolant should be changed at least every two years regardless of mileage.

1. Place your bike upright on a paddock stand. On a sports bike you may need to take off most of the fairing in order to access the radiator cap, header tank cap and drain bolt. Some drain bolts are located on the same side as the side-stand; if yours is, place the bike on the side stand in order to facilitate the draining process.
2. The majority of drain bolts are found on the lowest part of the cooling system, or on the housing of the coolant pump. For bikes without drain bolts, the lowest hose should be removed in order to drain. Be sure the coolant is cold before attempting this task.
3. Put some kind of tray or other receptacle under the drain bolt, then take off the radiator cap in order to relieve any system pressure and permit the coolant to exit with ease. Turn the drain bolt a few times to loosen it and make sure any sealing washer is loose too. Take off the bolt and washer.
4. After draining, clean the exit hole, the bolt and washer. Refit the bolt and washer. Replace the washer if it is damaged in any way. Ensure the bolt is closed tightly.
5. Prepare the coolant and the funnel. Be sure you have used distilled water if you are diluting your anti-freeze. You can use boiled tap water as an alternative – but as mentioned, do not use regular cold tap water, as it contains clogging and corroding minerals.
6. Insert the funnel in the radiator top and steadily fill with coolant. Pause regularly to enable any trapped air to escape. Purge any trapped air in the hoses by squeezing them gently. Fill coolant up to the point where the boom of the rad cap will be when fitted.
7. After refitting the radiator cap, pour coolant into the header tank, filling it to the point halfway between the upper and lower fill marks. If there are bleed bolts present, use them to release any air, being sure to re-fix them tightly.
8. Turn the engine over for a minute and check to make sure there are no leaks. Idling the engine in this way should release any remaining trapped air.
9. Take off the radiator cap and check that the coolant level is satisfactory. Top up as required. Check the header tank level too and if empty, repeat stage 8.
10. Idle the engine again – long enough for the cooling fan to engage – then turn off. Wait for the engine to cool, then check the header tank level once again, topping up as required.
11. Clean any coolant from the bodywork, as it can corrode plated metal parts. Use soapy water to wash down. Store any remaining coolant securely away from children and animals.

Note that coolant that is sold as antifreeze needs to be diluted with distilled water. The usual ratio is 50:50, but it’s worth checking on the container’s instructions. Otherwise, coolant comes as a premixed solution ready to pour straight in.