|
|
PEDAL PULSATION Pedal pulsation is caused by components that are loose, or beyond tolerance limits. The primary cause of pulsation are disc brake rotors with excessive lateral runout or thickness vari- NOTE: Some pedal pulsation may be felt during BRAKE DRAG Brake drag occurs when the lining is in constant contact with the rotor or drum. Drag can occur at one Drag is a product of incomplete brake shoe release. Drag can be minor or severe enough to overheat the Minor drag will usually cause slight surface char- ring of the lining. It can also generate hard spots in Severe drag can char the brake lining all the way through. It can also distort and score rotors and Common causes of brake drag are: cables. • Loose/worn wheel bearing. • Seized caliper or wheel cylinder piston. • Caliper binding on corroded bushings or rusted slide surfaces. • Loose caliper mounting. • Drum brake shoes binding on worn/damaged support plates. • Mis-assembled components. • Long booster output rod. may be related to a blocked master cylinder return BRAKE FADE Brake fade is usually a product of overheating caused by brake drag. However, brake overheating BRAKE PULL Front brake pull condition could result from: • Seized caliper piston • Binding caliper • Loose caliper • Rusty caliper slide surfaces • Improper brake shoes • Damaged rotor component are further causes of pull. A damaged A common and frequently misdiagnosed pull condi- tion is where direction of pull changes after a few As the dragging brake overheats, efficiency is so reduced that fade occurs. Since the opposite brake An additional point when diagnosing a change in pull condition concerns brake cool down. Remember REAR BRAKE GRAB OR PULL Rear grab or pull is usually caused by improperly adjusted or seized parking brake cables, contami- BRAKES DO NOT HOLD AFTER DRIVING THROUGH DEEP This condition is generally caused by water soaked lining. If the lining is only wet, it can be dried by BRAKE LINING CONTAMINATION Brake lining contamination is mostly a product of leaking calipers or wheel cylinders, worn seals, driv- 5 - 8 BRAKES XJ DIAGNOSIS AND TESTING (Continued) |