Brake Fluid

There are two styles of master cylinder reservoirs. One type has a wire bail holding the reservoir cover in place. These master cylinders are typically made from cast iron and the reservoir and cylinder are made as one piece. Clean the top of the cover and the surrounding area. Unsnap the bail and check the fluid level. You will find a rubber diaphragm attached to the underside of the cover. The diaphragm prevents dirt, water, or other contamination from entering the fluid.

If necessary, add fluid to bring the level to within 1/4 inch (6 mm) of the top of the reservoir. With disc brakes, the fluid level can be expected to fall as the brake pads wear. However, low fluid level may be caused by a leak, and a checkup may be needed. Install the cover and snap the bail back in place. Many late-model cars have a plastic reservoir that is mounted on top of the master cylinder.  This reservoir is transparent. It often has a "full" and "add" line on the side. The fluid level can be observed through the plastic without taking off the top. Plastic reservoirs have screw-on caps that may be removed to add fluid as shown below. You should add fluid to bring the level to within 1/4 inch (6 mm) of the top of the reservoir.