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Coolant expansion tanks

Durable and reliable coolant reservoir bottles for optimal engine cooling.

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Is your coolant overflow tank failing? Get in touch with Natrad for a replacement quote

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When do I replace the coolant overflow tank?

A damaged engine expansion tank needs to be replaced immediately to ensure your cooling system functions correctly. If you notice leaks, persistent low coolant levels, or an overheating engine, visit your nearest Natrad for expert advice.

The expansion tank in a cooling system captures the excess volume of coolant created when the radiator temperature rises, and allows it to return when the temperature drops. A failing expansion tank can lead to severe overheating and possible mechanical failure. Radiator overflow tanks, also known as overflow expansion tanks or coolant reservoir tanks, can become discoloured, brittle, contaminated with sludge, or even crack due to age and thermal cycling.

coolant reservoir bottle

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A qualified technician can correctly install a coolant expansion tank

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The largest range of OE and aftermarket cooling system parts in Australia

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National warranty supported by our network of radiator workshops

Find high-quality replacement coolant expansion tanks

Modern vehicle cooling systems are pressurised to ensure efficient thermal management. As the engine coolant heats up, it expands, creating pressure inside the radiator.

The coolant expansion tank holds excess coolant displaced as the pressure rises, returning it to the radiator when the temperature and pressure drops. The coolant expansion tanks supplied by Natrad help ensure that the pressure within the cooling system is controlled and that engine coolant is not lost during expansion.

Natrad stocks a wide range of cooling parts, including coolant caps, hoses, water pumps, suitable for replacements or upgrades.

Ask your local Natrad technician about a free cooling system inspection to see what parts may need replacing.

All vehicle cooling parts supplied by Natrad are covered by our national warranty, supported by Australia's largest network of radiator workshops.

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FAQs

  • Can I install a replacement coolant reservoir tank myself?

    If you have basic mechanical knowledge, installing a new tank is a fairly straightforward procedure. However, you need to be aware that many newer trucks, cars and SUVs require priming the coolant system according to the manufacturer’s instructions to prevent bubbles or air pockets forming.

    A Natrad technician can help you select a replacement coolant tank with the correct fittings for your vehicle, and they can install the new tank for you if required.

  • When does the coolant reservoir tank need replacing?

    Signs that a radiator expansion tank needs to be replaced include:

    1. Coolant is always low
    2. Coolant is leaking, resulting in steam, puddles, drips and a detectable odour
    3. Your car engine is overheating.

    Replacing a failing coolant expansion tank prevents severe overheating and potential engine damage. Visit Natrad for expert diagnosis and replacement solutions.

  • How much coolant should be in the coolant overflow tank?

    The car coolant overflow tank should never be completely full. Check levels when the engine is cold; coolant should be between the minimum and maximum markers. If levels are low, top up with the recommended coolant mix.

    If you suspect a coolant leak, a Natrad technician can diagnose the issue and recommend the best course of action.

  • What happens if I overfill the radiator expansion tank?

    If the coolant expansion reservoir tank is too full, it will overflow through the reservoir overflow tube when the engine heats up. Once the level drops enough, it will remain high but no longer overflow.

    If you notice that the coolant expansion tank overflows after being overfilled, check the coolant level again once the car has cooled to ensure that it hasn’t dropped too low.

  • How do I know if my expansion tank is the wrong size for my vehicle?

    Using an incorrectly sized expansion tank can cause pressure issues in your automotive cooling system. Signs that your expansion tank is not the right fit include:

    • Coolant overflowing too frequently or not returning properly to the vehicle’s radiator
    • Rapid coolant loss without visible leaks
    • Increased engine temperature or frequent overheating
    • Inconsistent coolant levels that fluctuate unpredictably

    If you’re unsure whether your expansion tank is correctly sized for your cooling system, visit Natrad for expert advice and a proper fitment check.

Contact Us

Do you have a leak in your cooling system? Ask a specialist about the right replacement coolant expansion tank for your car.

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