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How to Refill Your Car's Coolant

Tap each step to follow along in order.

  1. Check the reservoir markings

    Look at the translucent coolant reservoir in the engine bay and confirm the level sits between the LOW/MIN and FULL/MAX marks.

  2. Only check when the engine is cool

    Right after driving, or while the engine is still hot, the coolant is under high pressure and temperature. Never open the radiator or reservoir cap in that state, and always let it cool down first to avoid burns.

  3. Top off with the correct water-to-antifreeze ratio

    Coolant is typically mixed at around a 50:50 ratio of water and antifreeze. Too little antifreeze raises the risk of freezing in winter, while too much can reduce cooling performance, so it's best to follow the manufacturer's recommended ratio.

  4. Add coolant slowly

    Open the cap and pour in a little at a time, being careful not to overfill past the maximum mark.

  5. Suspect a leak if the level keeps dropping

    If coolant keeps running low with no obvious explanation, it may be leaking from the radiator, a hose, or the water pump, so it's worth having a shop take a look.

  6. Check the coolant's color too

    Healthy coolant is usually a clear green, pink, or another product-specific color. If it looks murky brown, that can be a sign it's due for a change.

Watch Out for the Risk of Burns

Because the reservoir is translucent, you can check the level without even starting the engine, but if the engine is hot, the system is under high pressure, and simply opening the cap can cause a burn. Always let the engine cool down fully before checking or refilling.

Check Your Cabin Air Filter While You're At It

While you're checking your coolant, it's worth also looking into replacing your cabin air filter. Keeping it fresh helps maintain a comfortable interior environment.

Frequently Asked Questions

Can I use plain bottled water in an emergency?

A small amount as a temporary emergency top-off is generally fine, but you should have it properly replaced with real coolant (a water-antifreeze mix) at a shop as soon as possible.

What happens if the coolant runs completely dry?

Continuing to drive without enough coolant can cause the engine to overheat and lead to serious damage, so if the warning light comes on, pull over safely right away.