Don’t Neglect Brake Fluid During Hotter Months

With the onset of warmer weather many Australian families hook up the caravan, camper, trailer, or boat and head off for long anticipated getaways.

When preparing for these trips, it’s important that the condition of your vehicle's brake fluid isn’t overlooked.

The fact is that the combination of high temperatures and increased braking demands on fully loaded and/or towing vehicles can swiftly reveal issues with older or contaminated brake fluid.

Despite the braking system being considered a closed system, it can gradually absorb small amounts of moisture over time through imperfect seals, microscopic holes in rubber hoses, or even if the brake fluid reservoir cap is left open for an extended period. This moisture can mix with the brake fluid, increasing its water content.

Having water in hydraulic fluid is problematic. It not only reduces the transfer force of the brake fluid, affecting the maintenance of pressure from the brake pedal to the calipers or drums but also lowers the boiling point of the fluid. Hot temperatures exacerbate the problem, especially in demanding driving conditions like towing.

If the brake fluid reaches its boiling point, bubbles can form in the brake system, resulting in a spongy brake pedal feel that delays braking response and reduces the force reaching the calipers or drums. Both scenarios contribute to longer stopping distances.

What does brake fluid do?

Brake fluid serves three secondary functions: lubricating moving parts within the braking system, transferring force from the master cylinder to the cylinders at the wheels and dissipating heat.

Like other fluids in a vehicle, brake fluid should be changed periodically to ensure it remains fresh and uncontaminated, optimising the braking system's performance.

Testing brake fluid

To assess brake fluid quality, owners or mechanics can use electronic brake fluid testers or basic strip tests that estimate moisture content. If replacement is necessary, the workshop will specify a fluid aligned with the vehicles specifications and recommend the appropriate DOT rating brake fluid.

What does a DOT rating mean in brake fluid?

DOT ratings indicate the fluid's wet and dry boiling points. The higher the DOT rating, the higher the boiling point and fluid longevity. DOT 4 fluids are widely used, with options like Bendix's high-performance Polyglycol DOT 3 and DOT 4 fluids meeting strict Australian specifications, making them an excellent choice for demanding summer driving.


Never add DOT 5 brake fluid to DOT 3 or DOT 4 as they are not compatible.

What happens if the wrong brake fluid is used?

Using an incorrect DOT rated brake fluid in your vehicle could impact seals and damage the braking system, possibly leading to brake failure.

Your local Repco Authorised Service centre is well placed to advise you on the health of your braking system and forms part of our 65 point vehicle inspection when you have your car serviced with one of our workshops.

Plus, when you have your vehicle serviced with one of our over 500 workshops across the country you’ll be covered by our Nationwide Warranty for additional peace of mind.

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