Bleeding (Brakes, Clutch, Cooling)

Bleeding means removing trapped air from a hydraulic brake or clutch system, a cooling system or an oil-injection line. Air compresses, so in brakes it gives a soft, spongy lever and less braking power.

For brakes, the basic method is: fill the master cylinder reservoir with the correct fluid (usually DOT 4), fit a clear hose from the caliper bleed nipple into a container, then repeatedly squeeze the lever, open the nipple, close it before releasing the lever and top up the reservoir. Repeat until clear fluid with no bubbles comes out. Vacuum bleeders and reverse-fill syringes make the job easier.

Never let the reservoir run empty during bleeding, keep brake fluid off paint, and change it every one to two years as it absorbs moisture. If the lever is still soft, check for leaks and worn seals.