What color is that warning light? Except for a few car models there is no warning light to tell you the brake linings are worn. Even when there is a light and sensors for that, they typically apply to front disc brakes, not rear drum brakes, and they for sure will turn on long before the linings start grinding metal-on-metal.
If the warning light is yellow, that is for the anti-lock brakes if your vehicle has them. That has nothing to do with lining wear. You start by having the stored diagnostic fault code(s) read. They will indicate the circuit or system that needs further diagnosis.
If the warning light is red, that turns on when there's a difference in pressure in the two hydraulic systems. Typically that's due to a leak. The parking brake can use the same light. Be sure the pedal is fully releasing. If your vehicle has a brake fluid level sensor built into the master cylinder reservoir, that can also turn on the red warning light. If the fluid level is low and there is no external leak, that indicates the front disc brake pads are very worn. Mechanics will never fill the reservoir during other routine service such as oil changes because they know that when the new pads are installed, the pistons have to be pushed back into the calipers to make room for them and that will push brake fluid back up into the reservoir. If someone filled it previously, installing the new pads will cause the fluid to overflow and make a mess.
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Sunday, January 13th, 2013 AT 11:02 PM