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How to Check Brake Fluid

Brake fluid is essential for safe braking. Here's how to check the level and condition in under 5 minutes.

Safety warning: Brake fluid is toxic and highly corrosive. Avoid skin and eye contact. Wear gloves if possible. Keep away from children. Brake fluid also strips paint, if it spills on bodywork, rinse immediately with water.

About Brake Fluid

Brake fluid transmits the force from your brake pedal to the brake callipers at each wheel. If the level drops too low, air enters the system and you'll lose braking effectiveness, a potentially dangerous situation. Brake fluid also absorbs moisture over time, reducing its boiling point and effectiveness. Most manufacturers recommend replacing it every 2 years.

Types of Brake Fluid

  • DOT 3, Older vehicles. Absorbs moisture quickly.
  • DOT 4, Most common in modern cars. Higher boiling point. Use this unless your handbook specifies otherwise.
  • DOT 5.1, High-performance vehicles. Highest boiling point. Glycol-based (NOT the same as DOT 5 which is silicone-based).

Always use the grade specified in your owner's handbook. Never mix types unless explicitly allowed.

Step-by-Step: How to Check Brake Fluid

  1. Make sure the engine is cold and the car is on level ground. The fluid level changes slightly with temperature.
  2. Open the bonnet.
  3. Locate the brake fluid reservoir. It's a small translucent plastic bottle on the driver's side towards the back of the engine bay, usually with a yellow cap marked with a brake symbol. The translucent walls let you see the level without opening it.
  4. Check the level. Look at the MIN and MAX marks on the side of the reservoir. The fluid should be between these two marks.
  5. Check the condition. The fluid should appear golden/amber or clear. Dark brown fluid is degraded and should be changed by a mechanic. Do not open the cap unless you need to top up.

If the Level Is Low

A very slight drop in level over a long period is normal as brake pads wear down. If the level is near or below MIN, this can mean:

  • Brake pads are worn (most common reason)
  • There is a leak in the braking system

Do not simply top up and ignore it. Have the brakes inspected by a mechanic.

When to See a Mechanic

  • Level is very low or near/below MIN
  • Fluid is dark brown (needs replacing)
  • Soft or spongy brake pedal
  • After any brake work (pads, discs, callipers)
  • Every 2 years as preventive maintenance