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Brakes
BRAKE SYSTEM INSPECTIONS
SHOULD TOP YOUR SHOP’S CHECKLIST OF PREVENTIVE MAINTENANCE ITEMS
Edited from an article by Gary Goms, ImportCar, December 2002
Squealing brakes are like a flashing warning light on the instrument panel: The sound alone indicates to the vehicle owner that the brakes need immediate attention. Of course, if the brakes happen to be newly installed, the owner may be doubly alarmed, thinking that the brake squeal represents another, even more expensive, brake failure.
 BRAKE INSPECTIONS
Too often in today’s market, the import vehicle owner assumes that having the oil changed at the local quick lube is equivalent to performing the preventive maintenance (PM) services outlined in his owner’s manual. Unfortunately, PM is more than just changing oil and putting on new wiper blades. Most import manufacturers, for example, recommend that the brakes be checked for wear at every third oil change or approximately at 15,000-mile intervals. If the vehicle is receiving its scheduled preventive maintenance (PM) service, as it should, worn brakes will be detected long before they become a safety hazard.
Import manufacturers usually are very specific in their scheduled maintenance recommendations. Some recommend that hardware like the brake caliper guides and parking brake cables be inspected and lubricated at specific intervals, while others may recommend flushing the old brake fluid at specified intervals. In any case, brake service should be easy to sell during a routine, PM-oriented vehicle inspection.
BRAKE SYSTEM EVALUATION
Evaluating the condition of brake system components begins with the customer interview. For example, is the brake warning light or the anti-lock brake system (ABS) warning light illuminated? Have the brakes developed a performance complaint such as pulling, grabbing, poor pedal response or brake shudder? Or does the consumer simply want his brakes serviced because they are noisy?
A good service writer realizes that many consumers can’t accurately articulate brake performance complaints. Most just know that the "Brakes are noisy" or that "The brakes just don’t feel right." Consequently, if any doubt about the nature of the complaint remains, the interview should be followed by a short road test. One or two low-speed stops should be enough to verify specific performance complaints like noise, pulling or brake shudder.
The first step in any visual inspection should be to inspect the condition of the brake fluid. Fluid that is dirty or opaque in appearance should be flushed out of the system. If the fluid appears rusty or moisture-contaminated, the complete hydraulic system, including the ABS, should be inspected for excessive corrosion.
Since many imports are now being driven well over 200,000 miles before the vehicle is scrapped, normally reliable parts like vacuum boosters and master cylinders will gradually become worn and unreliable. Consequently, it’s important to take vehicle mileage and condition into account when writing service recommendations on high-mileage vehicles.
To illustrate, start the engine and listen for a vacuum leak at the pushrod seal on the brake booster. If the engine idles roughly with the booster in the released or applied position, a leaking vacuum booster may be indicated. Similarly, if sludge or corrosion has accumulated in the master cylinder reservoir, the master cylinder should be replaced as preventive maintenance.
Brake fluid contamination is another problem that may otherwise go undetected without a visual inspection. Since many import owners and inexperienced lube bay mechanics often mistake the brake fluid reservoir for a remotely mounted power steering fluid reservoir, brake fluid can be contaminated with power steering fluid or other petroleum-based lubricant. Oil in the brake fluid is often indicated by poor pedal response and by swollen rubber seals on the master cylinder reservoir caps or lids. When brake fluid is contaminated with oil, brake hoses and brake parts containing rubber seals must be replaced.
 WHEEL AND TIRE INSPECTION
Too often, a brake inspection begins after the wheels are removed. A more thorough procedure is to begin with the vehicle lifted and the wheels installed. Uneven tire wear, for example, may indicate wheel alignment problems that contribute to a brake pull or a brake wandering condition. Wheels that don’t freely rotate may indicate sticking brake calipers or seized parking brake cables, or warped brake rotors.
During the preliminary inspection, wheels should be wobbled in the vertical plane to detect worn or misadjusted wheel bearings or worn ball joints, each of which may affect brake performance. Wheels should also be steered or wobbled in the horizontal plane to detect loose steering and suspension components or binding support bearings on the MacPherson struts. Next, the tires should be inspected to ensure that they are the same size, air pressure, tread style and state of wear. Last, wheels should also be inspected for vertical and horizontal run-out. In many cases of pedal pulsation complaints, the root cause can be a bent wheel or defective tire casing.
THE WHEELS-OFF INSPECTION
The wheels-off inspection should begin by visually inspecting brake hoses, ABS wheel speed sensors, brake caliper boots and brake rotors. Brake hoses, for example, often crack near the solidly mounted ends. If the brakes are worn metal-to-metal, it’s a sure bet that the ABS wheel speed sensors are coated with iron powder. If the vehicle has accumulated many miles, it’s also very likely that the caliper boots have become brittle or cracked with age.
Last, if the brake rotors exhibit detectable binding during rotation, the thickness should be measured before proceeding with an estimate of repairs. If runout is, for example, .005" or more, at least .010" to .015" of stock must be removed to clean up the runout condition, not to mention cleaning up wear grooves and parallelism issues. Many import rotors are considered expendable items and many others allow for very little stock removal, so evaluating the need for replacement is a critical step in the inspection and estimating process.
Last, check the boots on the constant velocity joints for cracking or leakage because the most economical time for the customer to have new or remanufactured axles installed is when the brakes are being serviced. Similarly, check the MacPherson struts for leakage or deterioration in the protective boots and rebound bumpers.
 GETTING THE SQUEAL OUT
Choosing quality parts and carefully assembling the new parts is the key to providing a quiet, safe and durable brake service. Since brake squeal obviously can be caused by metal-to-metal contact, it’s important to machine rotors as smoothly as possible. Using sharp cutting bits and slow tool feeds, followed by a light sanding or buffing after the cutting process, can reduce potentially troublesome metal tearing. Next, it’s important to clean machining dust from freshly machined brake rotors. Some shops go so far as to use soap and water to remove iron dust from the rotor surface, while others prefer using brake cleaner and a clean shop towel to remove harmful dust or oil contamination.
Cut-rate shops often cast pad shims and mounting hardware aside in their quest for speed, so it’s not unusual to see vehicles with noise complaints come in with these items missing. New mounting hardware is always a recommended option.
Next, it’s important to lubricate caliper guides when required. Several high-tech lubricants are available that adhere to the metal very well during high-temperature and wet conditions to reduce caliper sticking and the pads dragging, and subsequently glazing against the rotor.
Last, the choice of brake pads is very important. There are several brands of pads that are specifically compounded to reduce or eliminate brake squeal in import brakes. In addition, several automotive chemical manufacturers are producing pad-to-rotor lubricants that are designed to expedite pad break-in and eliminate noise.
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