chapter 32

CHAPTER 32

Disc Brake System

Removing and Inspecting Calipers

Research the procedure for removing the caliper in the appropriate service information. Loosen the bleeder screws slightly and then retighten them.

32-1


If the caliper is being rebuilt or a new caliper will be installed, it is good practice to flush the old brake fluid from the system at this time.

32-1


Use a brake pedal holding tool to slightly apply the brakes and block off the compensating ports in the master cylinder to avoid excess fluid leakage.

32-1


Remove the brake line or hose from the caliper. Be careful not to lose the sealing rings.

32-1


Push the caliper pistons back into their bores slightly. While many use a screwdriver as shown, a pry bar is a safer choice.

32-1


Remove the caliper assembly from its mountings.

32-1


Inspect the caliper for leaks or damage, including the piston dust boot. Determine any necessary actions.

32-1

Inspecting Caliper Mountings,Slides, and Pins

Clean the caliper mountings and slides/pins using equipment/procedures for dealing with asbestos/hazardous dust.

32-2

Inspecting Caliper Mountings,Slides, and Pins

Inspect the caliper mountings and slides/pins for wear and damage. Determine any necessary actions.

32-2

Inspecting Brake Pads and WearIndicators

Determine the type of wear indicator system utilized. Check that it is not contacting or nearly contacting the rotor.

32-3

Inspecting Brake Pads and WearIndicators

If the system is a sensor style, test the system to verify that the system is operational. Determine any necessary actions.

32-3

Checking Brake Pads

Remove the pads and retaining hardware. Inspect all pads, retaining hardware, and anti-noise shims for wear or damage.

32-4

Checking Brake Pads

Measure the remaining brake pad thickness and compare to specifications. Determine any necessary action(s).

32-4

Disassembling Calipers

Disassemble the caliper, following the service manual procedure.

32-5


Clean all of the caliper parts following the service manual procedure.

32-5


Inspect each of the parts for damage, rust, and wear.

32-5


Measure the caliper bore-to-piston clearance with a feeler gauge and compare to specifications. Determine any necessary actions.

32-5

Reassembling Calipers

Make sure the rotor has been properly installed on the hub/spindle and the hub surface is free of rust or dirt.

32-6


Reassemble the caliper assembly, following the manufacturer’s procedure.

32-6


Assemble the pads, hardware, and caliper on the caliper mountings using the specified lubricant. Lubricate all moving parts.

32-6


Reinstall the brake line fittings using two new copper washers (if equipped).

32-6


Tighten the brake line fitting and caliper bolts to the proper torque. Bleed the brakes following the manufacturer’s procedure.

32-6


Seat the pads by applying the brake pedal several times, not allowing the pedal to go all the way to the floor.

32-6


If the brake pedal is spongy, you will need to bleed the brakes of any remaining trapped air in the system.

32-6


Inspect the system for any brake fluid leaks, no matter how small.

32-6

Retracting and Readjusting Pistonson an Integrated Parking Brake

Research the procedure for retracting the caliper piston. Select the proper adapter or tool to match the caliper piston.

32-7


Install the tool and turn it in the direction that causes the piston to retract.

32-7


Continue turning until the piston is lightly seated at the bottom of its bore.

32-7


Make sure the dust boot is seated properly in its grooves.

32-7

Inspecting and Measuring DiscBrake Rotors

Research the procedure and specifications for inspecting the rotor. If you have not already done so, remove the caliper assembly, brake pads, and any hardware. Clean the rotor with approved asbestos removal equipment.

32-8


Inspect the rotor for hard spots or hot spots, scoring, cracks, and damage.

32-8


Measure the rotor thickness at the deepest groove or thinnest part of the rotor and compare to specifications.

32-8


Measure the thickness of the rotor in a minimum of five to eight places around the face of the rotor. Calculate the maximum thickness variation and compare to specifications.

32-8


Set up a dial indicator to measure lateral runout. Rotate the rotor and find the lowest spot on the rotor, then zero the dial indicator.

32-8


Slowly rotate the rotor to find the highest spot on the rotor. Read the dial indicator showing maximum runout.

32-8


Keep turning the rotor to make sure the dial indicator does not read below zero. If it does, rezero the dial caliper on the lowest spot. Keep turning the rotor to find the highest spot and reread the dial indicator. Compare all of your readings to the specifications and determine if the rotor is fit for service, is machinable, or needs to be replaced.

32-8

Removing and Reinstalling Rotors

Research the procedure for removing and reinstalling the brake rotor. If you have not already done so, remove the caliper assembly, brake pads, and any hardware. If the caliper mount straddles the rotor, remove it.

32-9


To remove the hubless-style rotor, mark the rotor for proper reinstallation.

32-9


If there are screws or speed nuts holding the rotor to the hub, remove them.

32-9


Remove the rotor from the hub.

32-9


To remove the hub-style rotor, remove the wheel bearing locking mechanism.

32-9


Remove the wheel bearing adjusting nut, thrust washer, and outer bearing.

32-9


Follow the steps of the inner bearing and grease seal removal procedure if the rear bearing must be removed.

32-9


To reinstall a hubless-style rotor, clean all mounting surfaces on the hub and rotor and remove any burrs.

32-9


Slip the rotor over the wheel studs.

32-9


If the rotor uses small screws to hold the rotor to the hub, reinstall those and tighten to the proper torque.

32-9


Spin the rotor to ensure it spins true and does not contact any other components such as the dust shield.

32-9


To reinstall a hub-style rotor, see the wheel bearing service skill drills in the Wheel Bearing chapter. Be sure to properly lock the adjustment nut in place once adjustment is completed.

32-9


Spin the rotor to ensure it spins true and does not contact any other components such as the dust shield.

32-9

Refinishing Hubless Rotors onVehicle

Research the brake lathe manufacturer’s procedure for properly refinishing the rotor. Mount the on-car brake lathe to the rotor after cleaning the rust and dirt from between the rotor and hub or adjusting the wheel bearing so there is no end play.

32-10


Perform the runout calibration on the brake lathe.

32-10


Adjust the cutting bits and cut off any lip at the edge of the rotor.

32-10


Make sure the cutting bits will not contact the rotor face, and move the cutting head toward the inner diameter of the rotor face. Set the cutting bits to the proper cutting depth for machining.

32-10


Install the anti-chatter device, if specified.

32-10


Engage the automatic feed and watch for proper machining action. If necessary, repeat this step until all damaged surface areas have been removed on both sides of the rotor.

32-10


If necessary, perform a finish cut on the rotor.

32-10


Remeasure the rotor thickness to determine if the rotor is above minimum thickness specifications.

32-10

Refinishing Rotors off Vehicle

Research the brake lathe manufacturer’s procedure for properly refinishing the rotor. Clean nicks, burrs, or debris from the mounting surfaces of the rotor including the centering hole.

32-11


Mount the rotor. Check that the rotor is running true on the lathe.

32-11


Install the anti-chatter band or anti-chatter pucks on the rotor.

32-11


Position the cutting head about one-quarter the way in from the outer diameter of the rotor. Turn on the lathe.

32-11


Set the cutting bits to the proper cutting depth for machining the ridge.

32-11


By hand, move the cutting head outward toward the ridge. Slowly remove the ridge.

32-11


Once the ridge is removed, run the cutting head all the way in to the inner face of the rotor.

32-11


Set the cutting bits to the proper cutting depth for machining the rotor face.

32-11


Engage the automatic feed on “fast” cut and watch for proper machining action. Some single-cut machines only have one cutting speed. If necessary, repeat this step until all damaged surface areas have been removed on both sides of the rotor.

32-11


If necessary, perform a finish cut on the rotor. This is usually done on “slow” speed.

32-11


Use sandpaper or a drill with a sanding pad to give the rotor faces a nondirectional finish.

32-11


Remeasure the rotor thickness to determine if the rotor is above minimum thickness specifications.

32-11

Inspecting and Replacing Wheel Studs

Inspect the wheel studs and lug nuts for damage. Look for signs of stretched studs, cross-threaded lug nuts, and broken-off studs. Determine if the stud can be removed with the flange on or off the vehicle.

32-12


To perform the drawing-in method, position the flange so the stud has clearance on the back side to be removed.

32-12


Remove any damaged studs with a hammer. Be careful not to damage any of the surfaces on the flange and hub, including the wheel speed sensor and tone ring.

32-12


Insert the stud in the hole in the flange and rotate it so that all of the flutes on the stud line up with the notches in the flange.

32-12


Place enough heavy-duty washers over the stud to prevent the lug nut from bottoming out on the threads.

32-12


Place the lug nut onto the stud, flat side in. Tighten it until the stud bottoms out in the flange. Inspect the threads on the stud and lug nut to make sure they did not get damaged.

32-12


To perform the hydraulic press method, remove the hub and wheel flange from the vehicle following the manufacturer’s procedure.

32-12


Use the press to push out any damaged lug studs.

32-12


Insert the new lug stud into the wheel flange hole. Line up the flutes on the stud with the notches in the flange.

32-12


Support the hub and flange so the press is pushing the stud straight into the flange.

32-12


Push the stud in until it bottoms out in the flange.

32-12


To complete the drawing-in method and the hydraulic press method, verify that each stud is fully seated in the flange.

32-12


Reinstall the hub and flange on the vehicle if it was removed.

32-12

Installing Wheels, Torquing LugNuts, and Making Final Checks

Start the lug nuts on the wheel studs, being careful to match up the surfaces.

32-13


Carefully run all of the lug nuts down so they are seated in the wheel.

32-13


Lower the vehicle so the tires are partially on the ground to keep them from turning while tightening the lug nuts.

32-13


Use a torque wrench to tighten each lug nut to the proper torque in the proper sequence.

32-13


Once all of the lug nuts have been torqued, go around them again, this time in a circular pattern to ensure that you did not miss any in the previous pattern.

32-13


If the vehicle was equipped with hubcaps and valve stem caps, reinstall them.

32-13


Check the brake fluid level in the master cylinder reservoir. Start the vehicle and check the brake pedal for proper feel and height. Check the parking brake for proper operation. Also inspect the system for any brake fluid leaks and loose or missing fasteners.

32-13

chapter 32

Documents

inspecting caliper mountings

caliper parts

caliper assembly

new caliper

inspecting brake pads

caliper bolts

caliper bore

caliper pistons