Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/636156
38 | February 2016 and the air to escape through the master cylinder compensating port, and the fuid in the reservoir to enter the bore of the master cylinder. Once air stops coming up into the reservoir, or the pedal becomes frm, apply light pressure to the pedal, and observe if the pedal continues toward the foor. When the master cylinder ports are plugged, and the air is bled out of the bore, the pedal should be high and hard under low pedal or high pedal effort. If the pedal sinks under either condition, the seal is damaged and the master cylinder should be replaced. ABS glitch after hub replacement? Here's a useful tip from Raybestos. This applies to all ABS-equipped vehicles. The ABS light may be on and/or false ABS activa- tion may occur following wheel bearing hub replacement on only one side of an axle. If you diagnose a bad hub bearing on one side of a vehicle and the ABS wheel speed sensor or tone ring is integral to the bear- ing, you may need additional repairs to restore proper ABS functioning. In many cases, replacing one hub bearing will cause the driver to feel ABS false activation when coming to a slow stop on dry pavement. False activation is usually described as a pulse in the brake pedal when not expected. The pulsation comes from the ABS valves cycling the supposedly locked- up wheel. This is due to the difference in signal strength from the wheel speed The Chassis Prior to replacing pads, the caliper pistons must be retracted in order to provide room for the new and thicker pads. Never use channel pliers directly against the piston surfaces. Place a spare pad against the pistons and use a C-clamp to compress, or use a dedicated piston compressor tool that engages the pistons with a fat plate. Photo courtesy of Raybestos Brakes