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When and Why You Should Bleed the Brake System

Many experts recommend bleeding the brake system when maintaining your brakes. The purpose of bleeding the brakes is to remove any trapped air from the brake lines.

If you’re maintaining your brakes, you might be wondering when it’s appropriate to bleed the brake system. This guide will help you with the art of bleeding the brakes.

When You Should Bleed The Brake System

Bleed brakes

Image Credit: DIYMyToyota

In normal operation, you do not need to bleed the brake system. Yet, there are some situations that will require bleeding it:

  • Completely worn brake pads: This causes the fluid level in the master cylinder to drop. If it drops too far, air gets into the brake system.
  • Disc brake caliper or drum brake cylinder replacement: This requires disconnecting the brake lines. When that happens, air will enter the brake lines.
  • Replacement of some other brake system components: A disconnected hydraulic part within the brake system causes air to get into the brake lines. The master cylinder is a good example.
  • Compressed caliper piston: Sometimes you need to open the bleeder valve to compress the piston while changing brake pads. This can allow air to enter the brake lines.

What If You Don’t Bleed The Brake System?

What happens when air gets into the brake lines and if you don’t bleed the brake system? You won’t have responsive brakes. You will experience these issues:

  • Spongy brakes
  • Longer stopping distances

Air stays in the brake system until you bleed the system. The caliper pistons need enough hydraulic pressure to clamp the brake pads against the rotor. Air bubbles lessen the hydraulic pressure and put a damper on your car’s braking performance.

So as a precaution, you want to bleed your brakes when it’s necessary.

An Overview Of How To Bleed The Brake System

Bleeding a brake system at home ranges from easy to impossible. The following things define the difficulty:

  • Whether your car has an ABS system or not: Non-ABS brake systems are easy to bleed. Many ABS brake systems are easy to bleed as long as no air has entered the ABS modulator.
  • Whether there’s air in the ABS modulator: If air has entered the ABS modulator, some brake systems can still be bled without any issues. Other systems will need a dealer or shop to use their scan tool to bleed the brakes.
  • Whether your ABS system can only be bled with a scan tool: A scan tool contains a program that cycles the ABS modulator valves. When the valves are positioned in a certain way, you can bleed the brake system. Some brake systems cannot be bled without a scan tool.

Before bleeding your Toyota’s brakes, it’s important to find out how difficult the job will be. That way, you can determine whether to do it yourself or bring your car to a shop.

Bleeding your brakes is a straightforward process. It involves pumping the brake pedal with your foot to force the air out.

Flushing The Brake Fluid

Flushing the brake fluid is not required by some OEM's, but it’s recommended by most mechanics. It’s a preventative measure that involves replacing the old brake fluid with new brake fluid. Brake fluid absorbs water over time, which can damage brake components. Any easy rule of thumb is to flush the brake fluid every time you change the rotors.

Written by Jason Lancaster