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How to check and top up coolant

Car coolant reservoir is filled with green coolant

Overview

Keeping your car’s coolant topped up is a simple maintenance task that helps protect your engine from overheating. Coolant circulates through the engine to keep it at the right temperature, especially during hot days or long drives. Checking it regularly and topping it up when needed can help your car run more smoothly and efficiently over time. Here’s how to do it safely and easily at home.

Safety tip: Always wear the appropriate safety equipment (safety glasses, gloves, ear muffs and a mask, for example) and always follow the instructions for the product or equipment.

Tools and materials

    Steps

    1Let the engine cool down

    Before getting started, it’s absolutely essential that the engine is completely cool. Make sure the car is parked on level ground and has been turned off for at least 30 minutes. Opening the coolant reservoir while it’s still hot can be dangerous, as built-up pressure can cause boiling liquid to spray out, risking serious burns. Give your vehicle plenty of time to cool down fully before you begin.
    Open the coolant reservoir

    2Locate the coolant reservoir

    Once the engine is safe to work on, open the car bonnet and prop it up with the support rod. The coolant reservoir is usually a semi-transparent plastic tank located near the radiator, and it often has a warning symbol or is labelled 'engine coolant'. On the side of the coolant reservoir, you’ll see level indicators marked 'low' and 'full'. Ideally, the coolant should be sitting somewhere between those lines. If the level is below the 'low' mark, it’s time to add more.
    Coolant reservoir showing the fluid level

    3Choose the right coolant 

    Before topping up, make sure you’re using the right coolant for your vehicle. Coolant for cars comes in different colours and formulations, and mixing the wrong types can damage your cooling system. If you’re not sure what to use, your vehicle’s owner manual will have the correct information. You can also use the existing coolant colour as a guide—just be sure to follow the instructions on the product for the correct ratio and usage.
    Choose the right coolant

    4Top up the coolant

    Carefully unscrew the coolant reservoir cap to release any pressure, and place a funnel in the opening. Slowly pour the coolant into the tank, making sure to pour steadily and avoid any spills. Keep an eye on the level as you go, stopping when the coolant reaches the 'full' line. Be sure not to overfill the reservoir, as the coolant needs space to expand when the engine warms up again.
    Top up the coolant through a funnel

    5Remove air bubbles and finish up

    Once the coolant is at the correct level, give the radiator hose a gentle squeeze or lightly tap the side of the reservoir. This helps any air bubbles escape, ensuring the coolant flows smoothly through the system. After that, replace the cap securely, check that everything is tightened and tidy under the bonnet, then close it up.
    Secure the radiator coolant hose

    6Now that you’ve checked and topped up your coolant

    Health & Safety

    Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.

    When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.