ALTRACO ELECTRONIC DISC BRAKE CALIPER Manuale di Servizio Scaricare il pdf

After studying this chapter, you will be able to:

Identify common disc brake problems.

Diagnose disc brake problems.

Remove and replace front disc brake calipers.

Remove and replace rear disc brake calipers.

Remove and replace disc brake pads.

Refinish disc brake rotors.

Chapter 13

Disc Brake

Service

209

Important Terms

Noise Grooving Silencer band Hot spots

Pulsation Heat-checking Rough cut Swirl grinding

Loaded calipers Bluing Finish cut Non-directional finish

Staking Arbor Oscillating Bedding-in

Scoring Rotor adapters

In Chapter 6, you studied the service of disc brake caliper

hydraulic systems. In this chapter, you will learn how to diag-

nose and service the disc brake system friction components.

Pad and rotor service is very similar for every kind of disc brake

system, varying only according to size, mounting method, and

whether the caliper has a provision for a parking brake.

Variations, where they occur, will be noted in the text.

Common Disc Brake Problems

The most common disc brake problems are noise and

pulsation. Common brake noise includes squeaks and

squeals from brake shoe and rotor contact. Disc brakes

commonly produce high pitched squeals or squeaks when

the brakes are applied. This is often caused by glazed or

worn pads, but may be the result of polished (overly

smooth) rotors, excessively hard pad material, or the wear

indicator contacting the rotor. A grinding or rubbing noise

when the brakes are applied may indicate the pad linings

are worn and the metal shoes are contacting the rotor. Clicks

and knocks are produced by loose pad-to-caliper contact.

Pulsation is a type of vibration. It is usually felt as a side-

to-side motion in the steering wheel, or an up-and-down

motion in the brake pedal, or both, when the brakes are

applied. Pulsation is usually caused by variations in the rotor’s

surface. Long use or excessive heat can cause the rotor to

develop thickness variations, high spots, or warping.

Pulsation is also caused by hard spots (places in the rotor

which have become overheated and lost their original finish).

If heavier than normal pedal pressure is needed for

braking, this may be caused by worn or excessively hard

210 Auto Brakes

Figure 13-1.

Troubleshooting chart listing problems that can occur with disc brakes.

Disc Brake Problems (All)

Condition Possible Causes

Rear Disc Brake Problems

High-pitch squeal only when brakes applied

High-pitch squeal only when brakes released

High-pitch squeal at all times

Metallic grinding when brakes applied

One pad worn more than the other

Brake pedal pulsates

Excessive pedal effort

Glazed linings or polished rotor.

Pad wear sensor contacting rotor, replace pads.

Splash shield contacting rotor.

Pads worn down to metal.

Sticking caliper.

Caliper piston or slides sticking.

Caliper misaligned.

Excessive rotor runout.

Normal ABS operation.

Glazed linings. If linings OK, problem is in power

booster system.

Vehicle rolls when in gear with parking applied

If resistance felt when moving, rear brakes OK.

If resistance is not felt, rear caliper pistons sticking or

parking brake cable misadjusted.

Vehicle rolls with parking brake applied Rear caliper pistions sticking.

Parking brake cable misadjusted.

brake pads. Another cause of a hard pedal is an over-

heated brake system. Overheated rotors and pads have a

poor coefficient of friction, meaning the pedal must be

applied much harder to have the same braking effect.

However, before assuming the cause of a hard pedal is the

disc brakes, check the brake hydraulic system and any

power assist units.

A spongy pedal can be caused by caliper and mount-

ing hardware flexing. This is usually not a problem unless

the vehicle is designed to operate with high hydraulic sys-

tem pressures. Extreme caliper or bracket wear, cracks at

the mounting points, or loose bolts can also cause a

spongy pedal.

Rear disc brake defects include all of those previously

mentioned, plus specific problems involving the parking brake.

Sticking pistons or cables are the usual cause of problems. The

parking brake can stick in the applied or released position.

Pads and rotors that wear out ahead of time are often

caused by driver habits, or severe usage, such as mountain

driving or trailer towing. If the pads are wearing unevenly,

check for a sticking piston or slide pins, misaligned caliper,

or flexing. Figure 13-1 lists common disc brake problems

and their causes.

Caliper and Pad Service

While calipers and brake pads are similar in basic

components and operation, there are many differences in

design. These differences are in the areas of mounting,

noise reduction clips and insulators, and fasteners. These

are addressed where applicable.

1 2 3 4 5 6 ... 10 11

Sommario

Pagina 1 - Disc Brake

After studying this chapter, you will be able to:KIdentify common disc brake problems.KDiagnose disc brake problems.KRemove and replace front disc bra

Pagina 2 - Replacement

and adjust the spindle nut and install a new cotter pin.Check that the rotor turns freely. Bearing service will becovered in more detail in Chapter 17

Pagina 3 - Pad Removal

11. Technician A says that a rough cut should be used toremove a small amount of metal from the rotor.Technician B says that a rough cut should not be

Pagina 4 - Rear Caliper and Pad Removal

Performing Disc Brake Service onABS/TCS Equipped VehiclesMany of the most common brake service procedures,such as pad replacement, rotor service, and

Pagina 5 - Rotor Service

KOn a few vehicles, an adapter bracket must beremoved before the caliper can be removed. On othervehicles, the caliper and bracket can be easilyremove

Pagina 6 - Checking Rotor Condition

Compare the new pads with the old ones to ensurethey are correct. Be sure to note whether the mountingsurfaces (metal shoe) portion is correct, and th

Pagina 7 - Turning Rotors

Ball-and-Ramp Caliper ServiceThe ball-and-ramp caliper assembly works by usingthree steel balls along matching tapered ramps to apply thebrake pads. T

Pagina 8 - Removing Hot Spots

Checking Rotor ConditionBefore removing the rotor from the vehicle, check itfor damage, warping, and proper thickness. Normal rotorwear patterns consi

Pagina 9 - Rotor Installation

Rotor RemovalTo remove the rotor, remove the caliper as explainedearlier in this chapter. Some rotors are held in place byscrew or bolt fasteners, or

Pagina 10 - Review Questions—Chapter 13

Chapter 13 Disc Brake Service 223Figure 13-30.A—An ASE certified technician turning a brakerotor. Always follow the tool manufacturer’s machining proc

Pagina 11 - 230 Auto Brakes

Figure 13-32.A vehicle powered, on-car brake lathe operating sequence. The procedures will vary between the various lathe manufacturers. 1—The vehicle

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