ALTRACO ELECTRONIC DISC BRAKE CALIPER Manual de servicio descargar pdf (Pagina 2)

Performing Disc Brake Service on

ABS/TCS Equipped Vehicles

Many of the most common brake service procedures,

such as pad replacement, rotor service, and wheel bearing

replacement, are not affected by the presence of anti-lock

brakes (ABS) or traction controls (TCS). If the lining or friction

service replacement procedures involve the wheel speed

sensors, treat them gently, and recheck the gap where appli-

cable. Do not drop or hammer on the sensor rings, or use

them to pry on other components. Do not replace any system

hoses with standard (non-ABS) hoses. The higher pressures in

these systems can rupture a standard brake hose.

Checking Caliper and Pad Condition

Calipers are usually trouble free. However, they can

occasionally develop external brake fluid leaks or sticking

apply pistons. Hydraulic system problems were discussed

in Chapter 6. If there are no hydraulic system defects, the

caliper is usually not a source of problems. However, the

caliper should be checked for wear, cracks (especially at

the mounting points), and torn dust boots.

Observing the pad thickness and rotor condition is

the quickest way to determine whether the pads should be

replaced. Uneven wear between the inboard and outboard

pads is a sign of a sticking caliper piston or slide. Uneven

wear on one or both pads indicates that the caliper is mis-

aligned with the rotor.

Note in Figure 13-2 that pad thickness can be visually

checked by observing the pad lining thickness through

openings in the caliper. However, this provides only a gen-

eral idea of pad thickness. If the pads have a wear sensor,

you can check the amount of clearance between the sen-

sor and the rotor. If there is any doubt as to pad condition,

remove the caliper and check by measuring the pads

against specified minimum thickness. Note the condition

of the rotor. If the rotor is scored or appears to have been

overheated, the pads need replacement. Also, make sure

the wheel turns freely. If the wheel will not turn easily, the

caliper piston may be sticking, or there may be a problem

with the wheel bearings.

Front Caliper Removal and Pad

Replacement

To remove the caliper, first raise and support the vehi-

cle in a safe manner. If a lift is not available, support the

vehicle at the frame with jackstands. Mark the wheel stud

closest to the tire valve stem with crayon to ensure the tire

is reinstalled in the same position. Then remove the tire

and rim.

If the pads are going to be replaced and no other

service is needed, it is not necessary to remove the caliper

hose. If the caliper uses an electrical pad wear sensor, dis-

connect the sensor electrical connector, Figure 13-3.

Use a small prybar, C-clamp, large adjustable pliers,

or other tool to lightly push the pads away from the rotor,

Figure 13-4. This will make caliper removal easier. If the

rotors and pads are badly grooved, the pads may need to

be moved back a considerable distance before they can be

removed.

On vehicles equipped with ABS systems, some man-

ufacturers recommend opening the bleeder screw to allow

fluid to escape, rather than pushing it back into the

hydraulic actuator and master cylinder. This minimizes the

chance of contamination, which could cause problems.

Check the service manual before proceeding.

Chapter 13 Disc Brake Service 211

Note: The following procedure is for

replacing the pads without overhauling the

caliper. If the caliper must be overhauled,

refer to Chapter 6.

Warning: Before proceeding, carefully check

the temperature of the hub and rotor

assembly. If the assembly feels hot, allow it

to cool, or use gloves to protect yourself from burns.

Figure 13-2.

Brake pad thickness can be checked on this

assembly by looking through the inspection hole in the caliper.

(Toyota)

Inspection hole

Pad

Shoe

Rotor

Figure 13-3.

A disc brake assembly which uses electric pad

wear sensors. (Land Rover)

Pad sensor

plug

Pad

Remove the fasteners holding the caliper to the spin-

dle. There are several methods of attaching the caliper to

the spindle:

On some vehicles, the caliper is held by bolts which

thread into the caliper and slide on the spindle

through steel sleeves or bushings, Figure 13-5. These

bolts can be standard capscrews, or may have round

heads with an internal Allen or Torx

fitting.

Other brake systems use bolts which thread onto the

spindle assembly. The caliper slides on these bolts

through hardened steel sleeves and/or bushings. See

Figure 13-6.

On some vehicles, the caliper is held in place by rub-

ber or metal clips or bushings. The bushings, also

called support keys, are in turn held by screws or

bolts, Figure 13-7. The fasteners can be removed and

the clips or bushings lightly tapped out to remove the

caliper. The fasteners shown in Figure 13-8 are

removed and the clips are lifted off to free the caliper.

212 Auto Brakes

Caution: If the pads will be reused, do not

damage them by prying. It is usually pos-

sible to pry on the metal shoe portion of the

pads to move them. On some calipers, the pads can

be loosened by pushing the caliper housing forward

with a large C-clamp.

Figure 13-5.

A—This illustrates Allen head mounting bolts

used on a brake caliper. B—Torx

head bolts and the bit

needed for removal and installation. (General Motors)

Torx

head

mounting

bolts

Bracket

Torx

socket

Allen head

mounting bolt

Ratchet

wrench

Figure 13-6.

A brake caliper that uses caliper guide pin bolts

that, when installed, thread into the spindle.

Figure 13-4.

Using pliers to lightly force the inboard pad and

piston away from the rotor. This allows for easier caliper

removal. (Pontiac)

Caliper

Rotor

Inboard shoe

and pad

Piston

Adjustable

pliers

Brake line

Suspension

strut

Caliper guide

pin bolt

1 2 3 4 5 6 7 ... 10 11

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