Motorcycle coolant should be changed at least every two years because its performance deteriorates over time. Aluminium corrosion or changes in the fluid-to-coolant ratio are the usual causes for this. The solution should be kept as alkaline as possible, which is why most coolants include specific ingredients to help achieve this. However, these become less effective over time.
Ensure you choose a coolant made for aluminium alloys, since all motorcycle engines are made of these. Most bikes have a coolant capacity of three to four litres, although this can vary. Most coolants are pre-mixed and ready to add, but some coolants are sold as pure antifreeze; these must be diluted with distilled water – usually at a ratio of 50:50.
You'll need a funnel and enough premixed coolant, or pure coolant and distilled water. Never use tap water or water that has not been distilled. You'll also need appropriate screwdrivers and Allen keys in order to remove the panels and fairings – enabling access to the main drain bolt. A tray for collecting the old coolant and some rags for any spillages are also necessary.
If you attempt to open the main drain bolt after the engine has been running, you run the risk of being scalded. This is because the system has become pressurised, causing the coolant to erupt.
You should be aware that antifreeze is highly toxic and should be kept away from children and animals.
You don’t have a spare hour to complete the task, or if you have a history of putting window cleaner in your coolant tank!
- 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.
- 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.
- Put some kind of tray or other receptacles 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
As long as the coolant contains ethylene glycol antifreeze, it can be used in either car or motorcycle.