Subaru Impreza 2003, Service Manual

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BR-78
BRAKE
GENERAL DIAGNOSTICS
21.General Diagnostics
A: INSPECTION
Trouble and possible cause Corrective action
1. Insufficient braking (1) Fluid leakage from the hydraulic mechanism Repair or replace (cup, piston seal, piston boot,
master cylinder piston kit, pipe or hose).
(2) Entry of air into the hydraulic mechanism Bleed the air.
(3) Excessively wide shoe clearance Adjust the clearance.
(4) Wear, deteriorated surface material, adhering
water or fluid on the lining Replace, grind or clean.
(5) Improper operation of master cylinder, disc cal-
iper, brake booster or check valve Correct or replace.
2. Unstable or uneven
braking (1) Fluid on the lining, drum or rotor Eliminate cause of fluid leakage, clean, or replace.
(2) Drum or rotor eccentricity Correct or replace the drum or rotor.
(3) Worn brake drum, or damage to the drum
caused by sand Correct by grinding, or replace.
(4) Improper lining contact, deteriorated surface
material, improper inferior material, or wear Correct by grinding, or replace.
(5) Deformed back plate Correct or replace.
(6) Improper tire inflation Inflate to correct pressure.
(7) Disordered wheel alignment Adjust alignment.
(8) Loosened back plate or the support installing
bolts Retighten.
(9) Loosened wheel bearing Retighten to normal tightening torque or replace.
(10) Trouble in the hydraulic system Replace the cylinder, brake pipe or hose.
(11) Uneven effect of the parking brake Check, adjust, or replace the rear brake and cable
system.
3. Excessive pedal
stroke (1) Entry of air into the hydraulic mechanism Bleed the air.
(2) Excessive play in the master cylinder push rod Adjust.
(3) Fluid leakage from the hydraulic mechanism Repair or replace (cup, piston seal, piston boot,
master cylinder piston kit, pipe or hose).
(4) Improperly adjusted shoe clearance Adjust.
(5) Improper lining contact or worn lining Correct or replace.
4. Brake dragging or
improper brake return (1) Insufficient pedal play Adjust play.
(2) Improper master cylinder return Clean or replace the cylinder.
(3) Clogged hydraulic system Replace.
(4) Improper return or adjustment of parking brake Correct or adjust.
(5) Weakened spring tension or breakage of shoe
return spring Replace the spring.
(6) Excessively narrow shoe clearance Adjust the clearance.
(7) Improper disc caliper operation Correct or replace.
(8) Wheel bearing faulty Replace the wheel bearing.
5. Brake noise (1)
(creak sound) (1) Hardened or deteriorated lining Replace the shoe assembly or pad.
(2) Worn lining Replace the shoe assembly or pad.
(3) Loosened back plate or the support installing
bolts Retighten.
(4) Loose wheel bearing Retighten to normal tightening torque.
(5) Dirty drum or rotor Clean the drum or rotor, or clean and replace the
brake assembly.
6. Brake noise (2)
(hissing sound) (1) Worn lining Replace the shoe assembly or pad.
(2) Improper installed shoe or pad Correct or replace the shoe assembly or pad.
(3) Loose or bent drum or rotor Retighten or replace.