Symptom Chart - Hydraulic Brake System

WARNING: This page is about a different car, the 2008 Mercury Sable, 2008 Ford Taurus X, and 2008 Ford Taurus. 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 and/or brake fluid leaks Parking brake Wiring, terminals and connectors High-speed controller area network (HS-CAN) bus Instrument cluster	REFER to INSTRUMENT CLUSTER (IC), MESSAGE CENTER, AND WARNING CHIMES article to diagnose the red brake warning indicator.
The brakes pull or drift	Tires	INSPECT the tires for uneven or excessive wear, and correct inflation. REFER to WHEELS AND TIRES article.
	Brake pads	INSPECT the brake pads for contamination, uneven taper or excessive wear, REFER to Brake Pads .
	Brake discs	INSPECT the brake discs, wheel hubs and axle shaft flanges for contamination or damage. INSTALL new brake discs, hubs or axle shafts as necessary. REFER to FRONT DISC BRAKE article for front disc brakes, REAR DISC BRAKE article for rear disc brakes, FRONT SUSPENSION article for front hubs and REAR DRIVE AXLE/DIFFERENTIAL article for the rear axle shaft.
	Brake calipers and/or guide pins	INSPECT the brake calipers and guide pins, REFER to Brake Calipers and Brake Caliper Guide Pins .
	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	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 Component Test.
	Hydraulic control unit (HCU)	INSPECT the HCU. REFER to VEHICLE DYNAMIC SYSTEMS article.
The brake pedal eases down slowly	Air in the system	BLEED the system. REFER to Brake System Bleeding .
	Brake master cylinder	CARRY OUT the Brake Master Cylinder Component Test.
	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 Pads .
	Brake calipers and/or guide pins	INSPECT the brake calipers and guide pins, REFER to Brake Calipers and Brake Caliper Guide Pins .
	Anti-lock brake control system	CHECK the anti-lock brake control system. REFER to VEHICLE DYNAMIC SYSTEMS article.
Excessive/erratic brake pedal travel	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 Calipers and Brake Caliper Guide Pins .
	Brake flexible hose	INSPECT the brake flexible hoses for swelling and damage. INSTALL new as necessary. REFER to FRONT DISC BRAKE article for front disc brakes or REAR DISC BRAKE article for rear disc brakes.
	Brake master cylinder	CARRY OUT the Brake Master Cylinder Component Test.
	Brake pads	INSPECT the brake pads for taper wear, REFER to Brake Pads .
	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.
Brakes drag	Parking brake component	REPAIR or INSTALL new components as necessary. REFER to PARKING BRAKE AND ACTUATION article.
	Brake caliper guide pins	INSPECT the caliper guide pins for correct operation. INSTALL new components as necessary. REFER to Brake Caliper Guide Pins .
	Brake caliper(s)	INSPECT the brake calipers. REFER to Brake Calipers . REPAIR or INSTALL new brake calipers as necessary. REFER to FRONT DISC BRAKE article for front disc brakes or REAR DISC BRAKE article for rear disc brakes.
	Brake booster	CARRY OUT the Brake Booster Component Test.
	Brake master cylinder	CARRY OUT the Brake Master Cylinder Component Test.
Excessive brake pedal effort	Insufficient engine vacuum for brake booster operation	CHECK engine vacuum. REFER to the Intake Manifold Vacuum Test in ENGINE SYSTEM - GENERAL INFORMATION article.
	Brake booster manifold vacuum hose	VERIFY engine vacuum at the booster. REROUTE, REPAIR or INSTALL new components as necessary.
	Brake booster	VERIFY engine vacuum at the booster. CARRY OUT the Brake Booster Component Test.
	Brake booster check valve	VERIFY engine vacuum at the booster. CARRY OUT the Check Valve Component Test.