Brake problems usually indicate the need for certain repairs or replacement parts, so here is a quick review of some common fixes:

LOW BRAKE FLUID This may be the result of worn disc brake pads, or it may indicate a leak in the brake system. If the BRAKE WARNING LIGHT is also on, most likely the problem is a leak (though the Brake Warning light may also come on if the master cylinder reservoir has a fluid level sensor). Leaks are dangerous because they can cause brake failures. The brake calipers wheel cylinders, brake hoses and lines, and master cylinder all need to be inspected. If a leak is found, the defective component must be replaced. Your vehicle should NOT be driven until the leak can be repaired.

LOW BRAKE PEDAL The brake pedal may be low if the shoe adjusters on rear drum brakes are rusted or sticking and not compensating for normal lining wear. Adjusting the rear drum brakes may restore a full pedal. But unless the adjusters are cleaned or replaced the problem will return as the linings continue to wear. Other causes include worn brake linings or a fluid leak.

SPONGY OR SOFT BRAKE PEDAL This is usually caused by air in the brake system, either as a result of improper bleeding, fluid loss or a very low fluid level. The cure is to bleed all of the brake lines using the sequence recommended for your vehicle. Another possible cause is a rubber brake hose that is "ballooning" when the brakes are applied.

EXCESSIVE BRAKE PEDAL TRAVEL Possible causes include worn brake linings front or rear (or both), misadjusted drum brakes, or air in the brake lines. This can be dangerous because the brake pedal may run out of travel before the brakes are fully applied. Pumping the pedal when you apply the brakes usually helps, but you need to diagnose and fix the problem.

PEDAL SINKS TO FLOOR This may occur while holding your foot on the brake pedal at a stop light. If the pedal goes slowly down, it means the master cylinder is not holding pressure. This is also a potentially dangerous condition because a worn master cylinder or a leak in the hydraulic system may cause the brakes to fail.

BRAKE PEDAL PULSATION Indicates a warped brake rotor (one that is worn unevenly). The rotor needs to be resurfaced or replaced. The faces of a rotor must be parallel (within .0005 inch on most cars) and flat (no more than .003 inches of runout as a general rule on most cars and trucks, but some cars cannot tolerate any more than .0015 inches of runout). Excessive runout can be corrected by resurfacing the rotors in place with an on-car brake lathe, or by installed special tapered shims between the rotors and hub to correct the runout.

SCRAPING NOISE FROM BRAKES Usually indicates metal-to-metal contact due to worn out disc brake pads (or shoes on rear drum brakes). Your vehicle needs a brake job now! In fact, it is overdue for a brake job. Your vehicle is also dangerous to drive in this condition because it may take longer to stop. The rotors and/or drums will likely have to be resurface or replaced because you waited too long to replace the pads and shoes.

BRAKE SQUEAL Can be caused by vibrations between the disc brake pads and caliper, or the pads and rotor. Harder semi-metallic brake pads tend to be noisier than non asbestos (NOA) or ceramic brake pads. The noise can usually be eliminated by replacing the old pads with new ones (ceramic pads are usually the quietest, but may not be available for some applications because the vehicle requires semi-metallic pads), and resurfacing or replacing the rotors. Installing noise dampening shims behind the pads, spraying the rotors with some type of aerosol brake noise control compound and/or applying a small amount of high temperature brake grease (never ordinary grease) to the backs of the pads can also help suppress noise. Also, if any pad mounting hardware such as shims or anti-rattle clips are missing, these should be replaced.

A growing number of late model cars are equipped with antilock brake systems that can precharge the brakes in anticipation of braking (to reduce braking reaction time), or actually apply the brakes automatically as a function of the collision prevention system (automatic braking).

Replacing a set of brake pads is a common brake repair procedure. But if not done correctly, it can cause problems. Brake systems are very sensitive to rust and corrosion and should receive a thorough cleaning when new pads are installed. Residual rust or corrosion left in critical areas can cause brake issues almost immediately.

A growing number of late model cars are equipped with antilock brake systems that can precharge the brakes in anticipation of braking (to reduce braking reaction time), or actually apply the brakes automatically as a function of the collision prevention system (automatic braking).

CAUTION: If you are replacing the brake pads on these vehicles, the braking system must be deactivated before you work on the brakes, otherwise the system may energize the brakes unexpectedly causing the caliper pistons to push outward with considerable force. This could pinch your fingers if they are between the pads and rotors. If the pads have been removed, the pistons can blow out of their calipers. This can happen even when the ignition and engine are off!

The antilock brake system can be deactivated by locating and removing the main power fuse for the ABS system, or by using a scan tool to temporarily deactivate the system. Disconnecting the battery also works, but this may cause loss of certain memory settings in various vehicle modules.