Symptom Chart - Brake System

WARNING: This page is about a different car, the 2009 Mercury Milan, 2009 Lincoln MKZ, and 2009 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.

Condition	Possible Sources	Action
The red brake warning indicator and the yellow ABS warning indicator are illuminated	DTCs in the ABS module	REFER to VEHICLE DYNAMIC SYSTEMS article to diagnose the ABS module.
The red brake warning indicator is always/never on	Brake fluid level switch Parking brake switch Wiring, terminals or connectors Instrument cluster Smart junction box (SJB)	REFER to INSTRUMENT CLUSTER (IC), MESSAGE CENTER, AND WARNING CHIMES article to diagnose the red brake warning indicator.
Vehicle pulls or drifts during braking	Brake calipers and/or guide pins Brake flexible hose Brake pads Brake discs	INSPECT the brake system components. REFER to BRAKE SYSTEM INSPECTION .
	Tires	INSPECT the tires for uneven or excessive wear, and correct inflation. REFER to WHEELS AND TIRES article.
	Suspension component and/or wheel alignment	INSPECT the suspension and CHECK the wheel alignment. REFER to SUSPENSION SYSTEM - GENERAL INFORMATION article.
Brake pedal goes down fast or eases down slowly	Brake fluid leaks and/or air in the system	INSPECT the system for leaks. REPAIR as necessary. FILL the brake master cylinder reservoir. BLEED the system. REFER to BRAKE SYSTEM BLEEDING .
	Brake master cylinder	CARRY OUT the BRAKE MASTER CYLINDER - BYPASS CONDITION Component Test.
	Hydraulic Control Unit (HCU)	INSPECT the HCU. REFER to VEHICLE DYNAMIC SYSTEMS article.
Brakes lock up under light brake pedal force	Brake pads	INSPECT the brake pads for uneven taper or excessive wear, REFER to BRAKE SYSTEM INSPECTION .
	Brake calipers and/or guide pins	INSPECT the brake calipers and guide pins, REFER to BRAKE SYSTEM INSPECTION .
	Anti-lock Brake control System (ABS)	CHECK the anti-lock brake control system. REFER to VEHICLE DYNAMIC SYSTEMS article.
Excessive/erratic brake pedal travel (low/spongy pedal)	Brake fluid leaks and/or air in the system	INSPECT the system for leaks. REPAIR as necessary. BLEED the system. REFER to BRAKE SYSTEM BLEEDING .
	Brake calipers and/or guide pins	INSPECT the brake calipers and guide pins, REFER to BRAKE SYSTEM INSPECTION .
	Brake flexible hose	INSPECT the brake flexible hoses during brake application. REFER to BRAKE SYSTEM INSPECTION .
	Brake master cylinder	CARRY OUT the BRAKE MASTER CYLINDER - BYPASS CONDITION .
	Brake pads	INSPECT the brake pads for taper wear, REFER to BRAKE SYSTEM INSPECTION .
	Brake pedal	INSPECT the brake pedal for binding, obstructions and correct installation. REPAIR as necessary. CHECK the brake pedal fasteners for correct torque. REFER to Specifications in HYDRAULIC BRAKE ACTUATION article.
	Anti-lock brake control system	CHECK the anti-lock brake control system. REFER to VEHICLE DYNAMIC SYSTEMS article.
Erratic brake pedal travel	Brake pedal	INSPECT the brake pedal for binding, obstructions and correct connection to booster rod. REPAIR as necessary. CHECK the brake pedal fasteners for correct torque. REFER to Specifications in HYDRAULIC BRAKE ACTUATION article.
Erratic brake pedal travel	ABS	CHECK the anti-lock brake control system. REFER to VEHICLE DYNAMIC SYSTEMS article.
Brakes drag	Parking brake component	REPAIR or INSTALL new components as necessary. REFER to PARKING BRAKE AND ACTUATION article.
	Brake caliper and/or guide pins	INSPECT the brake caliper and guide pins for correct operation. INSTALL new components as necessary. REFER to BRAKE SYSTEM INSPECTION .
	Brake booster Brake master cylinder	CARRY OUT the BRAKE MASTER CYLINDER - BYPASS CONDITION .
Excessive brake pedal effort	Insufficient engine vacuum for brake booster operation Brake booster manifold vacuum hose Brake booster Brake booster check valve	CARRY OUT the BRAKE MASTER CYLINDER - BYPASS CONDITION .
Excessive brake pedal effort	Brake pads	INSPECT the brake pads. REFER to BRAKE SYSTEM INSPECTION .