When slowly turning right into a parking spot or my driveway, I have a grinding noise. I can feel it in the brake pedal. It feels like it does when my anti lock brakes are engaged.
Sounds like a good time to inspect the brake pads and rotors. If you do not have the tools, now would be a good time to take it in for brake service.
BRAKE PAD SERVICE
- Remove and discard a portion of brake fluid from master cylinder.
- Raise and support vehicle, then remove wheel and tire assembly.
- Unclip speed sensor wiring from brake hose.
- Remove caliper as outlined in “Caliper Service” leaving brake hose connected.
- Secure caliper with wire so that caliper is not hanging with weight on brake hose.
- Remove pads.
- Reverse procedure to install.
INSPECTION
BRAKE LININGS
Remove both front wheels and inspect the brake discs, calipers and linings. (Wheel bearings should be inspected at this time and repacked if required).
Do not get any oil or grease on the linings. It is recommended that both front wheel sets be replaced whenever a respective shoe and lining is worn or damaged. Inspect and, if required, replace rear brake linings also.
If the caliper is cracked or fluid leakage through the casting is evident, it must be replaced as a unit.
BRAKE ROUGHNESS
The most common cause of brake chatter on disc brakes is a variation in thickness of the disc. If roughness, vibration and/or pedal pulsation are encountered during vehicle operation, the disc may have excessive thickness variation. To inspect for this condition, measure the disc at twelve points with a micrometer at a radius approximately one inch from edge of disc. If thickness measurements vary more than specifications allow, the disc should be replaced with a new one.
Excessive lateral runout of braking disc may cause a “knocking back” of the pistons, possibly creating increased pedal travel and vibration when brakes are applied.
Before inspecting runout, wheel bearings should be adjusted.
BRAKE DISC SERVICE
Servicing of disc brakes is extremely critical due to close tolerances required in machining the brake disc to ensure proper brake operation.
Maintenance of these close controls on friction surfaces is required to prevent brake roughness. In addition, surface finish must be non-directional and maintained at a micro-inch finish. This close control of the rubbing surface finish is required to avoid pulls and erratic performance and promote long lining life and equal lining wear of both lefthand and righthand brakes.
In light of the foregoing remarks, refinishing of the rubbing surfaces should not be attempted unless suitable precision equipment, capable of measuring in micro-inches (millionths of an inch) is available.
To inspect runout of a disc, mount a suitable dial indicator on a convenient part (steering knuckle, tie rod, disc brake caliper housing) so that the plunger of the dial indicator contacts the disc at a point one inch from the outer edge. If the total indicated runout exceeds specifications, install a new disc.
GENERAL PRECAUTIONS
- Grease or any other foreign material must be kept off caliper, surfaces of disc and external surfaces of hub, during service procedures. Handling brake disc and calipers should be done in a way to avoid deformation of disc and nicking or scratching brake linings.
- If inspection reveals rubber piston seals are worn or damaged, they should be replaced immediately.
- During removal and installation of a wheel assembly, exercise care so as not to interfere with or damage caliper splash shield, bleeder screw or transfer tube, (if equipped).
- Front wheel bearings should be adjusted to specifications.
- Be sure vehicle is centered on hoist before servicing any of front end components to avoid bending or damaging disc splash shield on full righthand or lefthand wheel turns.
- Before vehicle is moved after any brake service work, be sure to obtain a firm brake pedal.
- The assembly bolts of two caliper housings (if equipped) should not be disturbed unless caliper requires service.
CALIPER INSPECTION
Should it become required to remove the caliper for installation of new components, clean all components in denatured alcohol, wipe dry using lint-free cloths. Use an air hose, blow out drilled passages and bores. Inspect dust boots for punctures or tears. If punctures or tears are evident, new boots should be installed upon reassembly.
Inspect piston bores in both housings for scoring or pitting. Bores that show light scratches or corrosion can usually be cleaned with crocus cloth. However, bores that have deep scratches or scoring may be honed, provided the diameter of the bore is not increased more than .002 inch. If the bore does not clean up within this specification, a new caliper housing should be installed (black stains on the bore walls are caused by piston seals and will do no harm).
When using a hone, be sure to install the hone baffle before honing bore. The baffle is used to protect the hone stones from damage. Use extreme care in cleaning calipers after honing. Remove all dust and grit by flushing caliper with denatured alcohol. Wipe dry with clean lint-free cloth and then clean a second time in the same manner.
BRAKE BLEED
The disc brake hydraulic system can be bled manually or with pressure bleeding equipment. On vehicles with disc brakes the brake pedal will require more pumping and frequent inspecting of fluid level in master cylinder during bleeding operation.
Never use brake fluid that has been drained from hydraulic system when bleeding the brakes. Be sure the disc brake pistons are returned to their normal positions and that the shoe and lining assemblies are properly seated. Before driving the vehicle, inspect brake operation to be sure that a firm pedal has been obtained.