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What happens if you overfill your coolant?

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Updated 11 Oct 2019Rowan Johnstone
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Coolant is a fluid that is added to your engine that helps prevent it from overheating. If your engine gets too far above its normal operating temperature, some serious damage can be caused and in the worst case scenario, cause an engine to seize and require that it be replaced.

COOLANT

What does it really do?

The coolant tank, also known as the coolant overflow bottle, is designed to hold coolant when the fluid heats up. When this happens, the coolant expands and if it had nowhere to go, it could cause damage to hoses and the engine. The coolant bottle provides a place into which coolant can expand without causing damage. Coolant tanks have two marks on them indicating a minimum and maximum level. The minimum mark is the lowest amount of coolant your engine will need and going below this may cause overheating problems.

The coolant tank, also known as the coolant overflow bottle, is designed to hold coolant when the fluid heats up. When this happens, the coolant expands and if it had nowhere to go, it could cause damage to hoses and the engine. The coolant bottle provides a place into which coolant can expand without causing damage. Coolant tanks have two marks on them indicating a minimum and maximum level. The minimum mark is the lowest amount of coolant your engine will need and going below this may cause overheating problems.

On the other hand, overfilling your coolant tank above the maximum level when it’s cold will mean that there’s nowhere for the coolant to expand into once it heats up. If this is the case, any excess will need to be removed from the system and this can happen via an overflow hose, or a hose may become damaged and burst.

This is where the real dangers of overfilling your coolant lie. Hot coolant leaking throughout your engine bay can cause serious damage to wiring and electrical components.

If you do end up with a burst hose, your engine could be starved of coolant and cause some pretty big problems. A less serious side effect is the puddle of coloured liquid that will be pooling beneath your car, which in most cases is just an inconvenience.

DAMAGE

Will using the wrong type of coolant damage your engine?

If you’re not confident, or you just want to remove any room for error, let an experienced mechanic handle things. Coolant will be checked and topped up if necessary and they’ll also make sure the correct type of coolant goes into your car. Get a free quote through AutoGuru, it’s quick and easy.

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Written ByRowan Johnstone

On weekdays Rowan can be found in the AutoGuru office, driving content and growth with the rest of the marketing team.

On weekends you’ll probably find him in the garage with his father restoring a 1958 Ford Star Model Customline or enjoying a cruise through the Gold Coast hinterland on his Suzuki GSX-R600.

Despite his passion for being behind the wheel (or handlebars), Rowan looks forward to the day when he can commute to work in his own driverless car.