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The Importance &
Function of Brake Fluid

Brake fluid is a type of hydraulic fluid used in hydraulic brake and hydraulic clutch applications in vehicles. It is used to transfer force into pressure, and to amplify braking force. Simply stated, when you apply your foot to the brake pedal, brake fluid transfers this force into pressure to the front and rear brakes and stops the vehicle. It works because liquids are incompressible.

What causes Brake Fluid to become contaminted?

Brake fluids must have certain characteristics and meet certain quality standards for the braking system to work properly. Brake fluid is subjected to very high temperatures, especially in the wheel cylinders of drum brakes and disk brake calipers. It must have a high boiling point to avoid vaporizing within the lines. Vaporization is a problem because vapor is highly compressible relative to liquid, and therefore negates the hydraulic transfer of braking force which will result in the brakes failing to stop the vehicle.

Most brake fluids used today are glycol-ether based. Glycol-ether (DOT 3, 4, and 5.1) brake fluids are hygroscopic, which means they absorb moisture from the atmosphere. Glycol based brake fluid starts to absorb moisture from the moment it is put in the hydraulic brake system or exposed to the air. The fluid attracts moisture through microscopic pores in rubber hoses, past seals, and exposure to the air. The problem is obviously worse in wet climates where humidity is high.

Why does Brake Fluid need to be flushed?

Brake fluid is designed to protect the metals used inside components such as calipers, wheel cylinders, master cylinders, and ABS control valves. The fluid must also protect against corrosion as moisture enters the system. Additives (corrosion inhibitors) are added to the base brake fluid to help accomplish this.

The corrosion inhibitors in brake fluid degrade over time. Degraded inhibitors in conjunction with the presence of excessive water cause corrosion in the braking system. After only a year of service, the brake fluid in the average vehicle may contain as much as two percent water. After 18 months, the level of contamination can be as high as three percent. After several years of service, it is not unusual to find brake fluid that contains as much as seven to eight percent water.

Excessive water content will decrease the boiling point of brake fluid and increase the risk of vapor lock. The compression of a vapor lock when applying the brake pedal can lead to total hydraulic brake system failure. Water also promotes corrosion of important metal brake components.

When Do I Need
a Brake Fluid Flush?

Corrosion and rust can cause structural damage to your braking system, leading to costly repairs. Regular brake fluid service can prevent these deeper system issues from occurring. Brake fluid flushes are recommended every 50,000 kilometers or 2 years, depending on your driving and braking patterns.

The Different Colours of Brake Fluid

LEFT: Clean brake fluid with low moisture and debris content. Does not require a brake fluid flush.

MIDDLE: Staring to become contaminated. Recommend to perform a brake fluid flush in the near future

RIGHT: Severely contaminated. Highly recommend to perform a brake fluid flush as soon as possible.

  • Brake Fluid Flush from $115

    During a brake fluid flush, a licensed technician will: vacuum old brake fluid from the reservoir, clean debris from the reservoir, fill reservoir with new, OEM fluid, vacuum 100% of the old fluid from the vehicle, top-up brake fluid as required, and ensure proper operation of hydraulic brake system.

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