Brake fluid is leaking

Your brakes are the most important safety system on your vehicle. It’s all too easy to take them for granted, but if they were to fail even once, the results could be catastrophic. Most automotive brake systems are hydraulic, which means that pressurized fluid is sent through the lines from the master cylinder to the calipers and drums in order to activate the pads/shoes and slow down the car. If your brake fluid is leaking, it’s a sign that there’s something seriously wrong.

How this system works:

Your brake system is both simple and complex. There are a number of parts required to make it work properly, but the underlying concept is not that difficult to understand. Your master cylinder is the heart of the system – it is responsible for both boosting brake performance (via the brake booster onto which the master cylinder mounts), and for holding and sending brake fluid through the system.

In a nutshell, your brake system works like this: You press the brake pedal, which activates the master cylinder. It pushes fluid into the lines and down to the calipers. The fluid pressure forces the calipers to close, squeezing the rotor between the brake pads. This creates drag and friction, slowing down the car.

However, if fluid is leaking from somewhere in the system, it could mean that you’ll have insufficient fluid for proper brake operation.

Common reasons for this to happen:

  • Worn Brake Pads: If you suspect fluid is leaking because the level in the reservoir is low, it might be nothing more than worn pads. As the pads wear, more fluid is held in the system (because the caliper piston remains farther out due to the reduced pad material).
  • Damaged Master Cylinder Reservoir: Over time, the plastic reservoir attached to your master cylinder becomes brittle due to heat exposure. It can eventually crack, allowing brake fluid to seep out and down the back of the engine.
  • Damaged Bleeder Valve: Each caliper has a bleeder. These valves allow mechanics to bleed air out of the lines, but they can become damaged (or can be knocked loose or even left loose after inexpert service).
  • Damaged Brake Line: Your car has both rubber and steel brake lines that carry fluid to and from the master cylinder. Both types are prone to wear and can be punctured. If this occurs, fluid will steadily leak out of the line.
  • Failed Wheel Cylinder: On drum brakes, one of the most likely culprits is the wheel seal. These will fail over time and through normal wear and tear, eventually weeping brake fluid.
  • Failed Piston Seal: The piston in your caliper is activated by fluid, and it’s a moving part, which means a seal is necessary to keep the fluid inside while allowing the piston to move. If the seal is damaged (cracked or punctured), it will leak brake fluid.

How important is this service?

Without an operational brake system, your car cannot be safely driven. Leaking fluid is cause for concern – if the fluid level drops below a certain level, the brakes will not work. It’s essential to have your brake system inspected during normal maintenance, and to pay close attention to the fluid level in the reservoir. Any leaks should be immediately inspected and repaired.