Wrench Tip Wednesday: Flushing the Cooling System

Wrench Tip Wednesday: Flushing the Cooling System

Flushing the coolant out of your dirt bike should be a yearly maintenance deal or if you are changing brands. Different coolant brands should never be mixed. Chemical reactions can happen with lots of possibilities of damaging the bike. Automotive coolant can be used but may require more maintenance verse specific motorcycle/powersport coolant.

Things to look for when looking at different brands; Propylene Glycol (biodegradable and non-toxic) and should not contain any silicate or phosphates. If the coolant does, it can break down, build a thick layer, and the engine could potentially overheat or it can eat the water pump seals. Engine Ice is one of the two popular brands we sell. It is Propylene Glycol, premixed with deionized water to eliminate impurities, and in a pinch water can be added. The other customer favorite is Evans, also Propylene Glycol with high boiling point, containing no water. The major downside to Evans is that it cannot be mixed with water or anything!

NEVER change coolant on a hot bike. NEVER remove the radiator cap on a hot bike. When coolant is heated, it is under pressure and can potentially spray and burn your skin off. To drain the coolant, locate the drain plug bolt. Generally, it is found on the water pump housing. The bolt will have a copper washer on it, do not lose this. After the drain plug is removed, remove the radiator cap. Let it completely drain out. It can be messy trying to get the pan in the right spot to catch it all. Pro tip – if you change coolant regularly and use a non-corrosive formula you will most likely not need to flush unless you are changing brands.


Put the drain plug back in. Pour water into the radiator. Install radiator cap. Start the dirt bike, run until operation temperature. Let it cool, then drain it out. Install new coolant and be sure to check for leaks.

While in the cooling system, it is a good idea to go ahead and check the water pump for dirt or corrosion. If the impeller can be moved up or down, bearings and seals are needed and maybe a water pump shaft. Oil leaking into the water pump can also be sign of bearings and seals in need of being replaced.

Winter is the perfect time to do this to help ensure the coolant won’t freeze and the bike will be ready for the upcoming riding/race season!


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