Brake Bleed
What is the brake hydraulic system?
Nearly all passenger vehicles use the very reliable hydraulic brake system. At a minimum, the system is composed of a master cylinder, which pumps brake fluid through brake lines, wheel cylinders or brake calipers that actuate the brake pads or shoes, and brake rotors or brake drums that rotate with the wheel until acted upon by the pads or shoes. In order for the brake system to function properly and reliably, the brake fluid must be serviced regularly, including flushing and bleeding the brake fluid to prevent corrosion, air, or water from causing damage in the brake system.
Which should I get, a brake fluid bleed or a brake flush?
The brake bleeding process involves manually pumping enough new fluid through your brake lines to eliminate any air that may be in them. This can be done either by one person, using an external hand pump, or by two people, using the car’s brake pedal. The vehicle’s four brakes are bled individually, using a bleeder screw found on each caliper or wheel cylinder. People with good knowledge of hydraulic braking systems can learn how to bleed brakes themselves, or a mechanic can handle it instead.
The brake flushing process goes a step beyond. Flushing replaces all of your old brake fluid with clean, new fluid. This procedure is often done with a powered flushing machine, which attaches to the brake fluid reservoir where the cap would normally screw on. New brake fluid is forced through the entire hydraulic system until the fluid that exits the system is clean. Flushing gives you all new brake fluid throughout your braking system.
Here are a few guidelines on whether you should bleed or flush your brakes when servicing them:
What does the manufacturer recommend? Check your owner’s manual or service booklet for the manufacturer’s suggestions on when and how to service your brakes. If there’s no recommendation for flushing your brakes, it’s usually not necessary, especially if you have followed the recommended service intervals and the fluid looks translucent or clear, not dark and murky.
Are there signs of a braking problem? Have you noticed that your brake pedal feels squishy? Does your vehicle require a longer distance to stop lately? Is your brake fluid dark, or does it have particles and debris floating in it?
If you notice any of these symptoms, get your car to your mechanic immediately. Have your braking problem diagnosed and repaired right away, before things get worse and you are totally unable to stop. If your fluid has deteriorated and needs replacing, then a flush is an appropriate step toward restoring the effectiveness of your brakes.