Check and top up coolant

A liquid-cooled engine pumps coolant (water mixed with antifreeze and corrosion inhibitor) through passages in the engine and through a radiator, where air takes the heat away. Most bikes have a small plastic reserve tank (expansion tank) with UPPER and LOWER marks. You check and top up there, not at the radiator cap. A level that keeps falling means a leak, inside or outside the engine.

Safety

• Check only when the engine is cold.
• Never open the radiator cap on a hot engine. The coolant is under pressure and above boiling point; it can spray out and scald you.
• Coolant is poisonous and tastes sweet. Wipe up spills, keep it away from children and animals, and store it in its labelled bottle.
• Coolant on the tyre is slippery. Wipe it off.

You need

• Coolant of the type your manual names. Do not mix different types or colours unless the maker says they are compatible.
• Use distilled or demineralised water if the coolant is a concentrate. Hard tap water leaves scale. Plain water alone gives no corrosion protection and can freeze in cold places.

Steps

1. Park on level ground, engine cold, bike upright (on the centre stand or held straight).
2. Find the reserve tank. It may be behind a side cover; remove the cover if needed.
3. Read the level against the UPPER and LOWER marks.
4. If the level is below LOWER, remove the reserve tank cap (not the radiator cap) and add coolant to the UPPER mark.
5. Refit the cap and the side cover.
6. Look at the coolant colour. Rusty brown, oily or murky coolant needs replacing: see Replace the coolant.
7. Look under the bike and round the radiator, hoses and water pump for wet patches or dried coloured crust.
8. Write down the date and how much you added.

Check your work

• Level at the UPPER mark when cold.
• Cap fitted firmly, no spills left.
• At the next check the level is about the same.

If it did not fix the problem

• You need to add coolant often, or the tank was empty: Coolant is leaking and Find a coolant leak.
• No visible leak but the level falls, with white smoke or milky oil: possible head gasket; see White smoke or steam from the exhaust.
• Level correct but the engine overheats: Liquid-cooled engine overheats.