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1、Welcome To,Brake System Operation & Diagnosis,SECTION 18,Objectives,List the advantages of disc brakes. List disc brake components and describe their functions. Explain the differences between the three types of calipers commonly used on disc brakes.,continued,Objectives,Describe the two types of pa
2、rking brake systems used with disc brakes. Describe the causes of common disc brake problems. Explain what precautions should be taken when servicing disc brake systems.,continued,Objectives,Describe the general procedure involved in replacing disc brake pads. List and describe five typical disc bra
3、ke rotor problems.,continued,Disc Brake Advantages,Resistance to heat fade Resistance to water fade Increased straight-line stopping ability Automatic adjustment,continued,Disc Brake Components,Rotor Including hub on some vehicles Caliper assembly Including piston, seal, and dust boot Pads Antisquea
4、l hardware Attaching hardware,continued,Designs,Fixed caliper The caliper is bolted in a fixed position and does not move.,continued,Designs,Floating caliper The caliper moves on locating pins.,continued,Designs,Sliding caliper Similar to the floating type, but it does not use pins.,continued,Calipe
5、r Self-Adjustment,As the disc brake pads wear, the seal allows the piston to move farther out to adjust automatically for the wear, without allowing fluid to leak. Since the brake pads need to retract only slightly after they have been applied, the deformation of the pistons square-cut seal retracts
6、 the piston only slightly into its bore.,continued,Caliper Self-Adjustment,continued,Common Disc Brake Problems,Pulsating pedal Commonly caused by warped rotors Spongy pedal Commonly caused by air in the system Hard pedal Commonly caused by a power booster problem Dragging brakes Commonly caused by
7、sticking or seized pistons,continued,Common Disc Brake Problems,Grabbing brakes Commonly caused by contaminated brake linings Noise Commonly caused by improper pad installation Pulling Commonly caused by one wheel doing more of the braking,continued,Pre-Service Checks,Tires - for wear and improper i
8、nflation Wheels - for bent or warped rims Wheel bearings - for wear or looseness Suspension components - for wear or looseness Brake fluid - level Hydraulic system - for leaks,continued,Brake Pad Wear Indicators,Disc Pad Wear Sensors Some brake shoe pads have wear sensing indicators. The 3 most comm
9、on designs are audible, visual (indicator light), and tactile (touch).,continued,Caliper Service Tips,Carefully use air to remove the caliper piston from its bore,continued,Caliper Service Tips,Carefully remove the dust boot and piston seal,continued,Caliper Service Tips,Make sure the correct calipe
10、r is mounted on the correct anchor plate. Lubricate rubber insulators with silicone dielectric compound. If copper washers are used, always use new ones.,continued,Caliper Service Tips,Fill the master cylinder and bleed the hydraulic system. Check for leaks under maximum pedal pressure. Road test th
11、e vehicle.,continued,Common Rotor Checks,Lateral runout or side to side wobble,continued,Common Rotor Checks,Lack of parallelism or variations in the rotor thickness (check in 8 places),continued,Common Rotor Checks,Minimum thickness Scoring Heat checking (bluing) Rusty rotor Collapsed vents Mountin
12、g flange rust,continued,Rear Disc Park Brakes,A rear disc/drum or auxiliary drum parking brake arrangement uses the inside of each rear wheel hub and rotor assembly as a parking brake drum. Other designs have mechanisms that force the pads against the rotor mechanically. Common methods include a bal
13、l-and-ramp arrangement and high-lead screws.,continued,Rear Disc Park Brakes,A rear disc/drum brake assembly,continued,Summary,Disc brakes offer four major advantages over drum brakes: resistance to heat fade, resistance to water fade, increased straight-line stopping ability, and automatic adjustme
14、nt. The caliper assembly includes cylinder bores and pistons, dust boots, and piston hydraulic seals.,continued,Summary,Fixed calipers do not move when the brakes are applied. Floating calipers slide back and forth on pins or bolts. On some rear disc brake systems, the inside of the rear rotor is us
15、ed as the parking brake drum.,continued,Summary,Some rear disc parking brakes have a mechanism that forces the pads against the rotor mechanically. Disc brakes should be checked periodically or whenever the wheels are removed. Disc brake rotor defects include lateral runout, lack of parallelism, scoring, heat checking, and rust.,
