Auto Service World
Feature   April 1, 2010   by Auto Service World

Helping Customers Avoid the Incomplete Brake Job

Knowledge Building:

Brake jobs make up the largest single category of work that most shops perform. However, in their haste to get the car off the hoist and the customer back on the road, sometimes technicians take shortcuts. And if the customer ends up back in the shop complaining, you are bound to hear about it.

Often it is the brake friction that can take the heat for noisy or uncharacteristic braking; while this can be true if the formulation is not right for the application, often other factors are at play.

It is commonly accepted that the most frequent source of car owner unhappiness is noise; hence it is the most common source of the unhappy calls you might get from your customers.

Here are some questions you should ask them to avoid a repeat. In fact, it might be helpful if they were to ask themselves these questions when a brake job boomerangs.

1) Brake Pad Facts

While certainly not always the case, as the subsequent points of this article will indicate, noise can result from brake pad-related issues.

Shims have been found to cure many post-repair noise problems, and many pads have them integrated into the backing plate or included as part of the set. If the latter, technicians should not neglect to install them.

Pads almost always need to be bedded in, though it is less critical these days due to special coatings that are added to many pads (and rotors). Nonetheless, bedding-in is important and should the rotor not provide a good mating service, the process, and the noise that may result, could cause customer dissatisfaction.

According to some manufacturers, bed-in times can be extended if the rotor is not turned or surface is not flat, perhaps up to 800 km. Given this possibility, it is wise to ensure rotor surface finish and runout are acceptable.

2) Hard Facts about Hardware

One of the key shortcomings of a brake job gone bad is failing to replace brake hardware.

Manufacturers have noted that in cases where hardware is supplied with brake friction, the hardware sometimes returns unused alongside the brake pads in warranty claims. This isn’t always the case, but in such instances it is clear that the technician involved has not understood the importance of replacing hardware.

Disc brake hardware includes anti-rattle clips and springs that secure pads in the caliper and prevent brake noise; guide pins on floating calipers that support and attach the caliper to the anchor plate; guide boots that protect them from corrosion; bushings and insulators that cushion caliper movements and help eliminate brake noise; and the caliper support key on some floating calipers that is used to locate and support it.

In today’s brake systems (actually in those produced for some time now), smaller rotors and lighter components have subjected hardware to significant heat cycling. Virtually any parts that are designed to hold brake parts in place have a useful life only as long as they can maintain sufficient spring tension.

3) Drum, Drums, Drums

While the disc-disc brake system has become much more common, there are still quite a few disc-drum-equipped cars, new and old, on the roads.

And while drum brakes may be more difficult to service in some respects, they can still suffer from creeping failures that can result in an unhappy customer.

Once again, hardware can be at fault.

Drum brake hardware includes shoe return springs that retract shoes from the drum; hold-down springs that hold shoes on the backing plate; hold-down pins that hold the shoe in place on the backing plate; and the automatic adjuster, which compensates for friction material and drum wear.

Fatigue, corrosion, or dirty hardware can cause drum brake performance to be less than ideal.

4) A Chemical World

Significantly, proper brake service also includes proper use of high-temp silicone lubricant.

As with hardware, it is not uncommon for items being returned for dragging, premature wear, or binding to arrive completely dry, without any evidence of lubricant having been used. Make sure to look up and use only the recommended caliper lube procedure. Keep in mind that all manufacturers have very specific lubrication procedures. This lubrication is necessary to prevent vibration-induced noise.

Even when hardware is replaced and the proper lube employed, a caliper or set of pads may not be free to move, owing to a buildup of corrosion on a bracket. Some times this can be very stubborn to remove, requiring a chisel or perhaps even the use of a rotary abrasive and a drill.

The key point is that all surfaces must be clean, in good condition, and properly lubricated if they are to allow the caliper and pads to move freely.

Failure to employ these procedures has become grounds to refuse warranty claims, which is something that all professional counterpeople should be aware of.

5) Rotor Realities

It should seem obvious that pads must mate properly with rotors to provide proper braking performance, but the surface of the rotor must also be considered.

In addition to the requirement that runout be within specifications, the surface finish must also be rough enough to provide a good surface, but not so rough as to cause pads, particularly semi-metallic formulations, to “track.” This condi-tion, where the pad follows the direction of finish outward then snaps back to the inner radius under tension from hardware, can cause a clicking noise.

The solution is to ensure a non-directional finish of a very fine nature, between 10 and 50 microinches. Advisories call for using 120 grit abrasive paper for the final finish.

While ready-to-install rotors have entered the market, in most cases new rotors should be washed with soap and hot water before installation, as solvent-type cleaners may not remove all machining dust, and because drying with com-pressed air can result in oil contamination of the friction material.

For rotors being reused, there are a number of cleaning options. In any case a clean rotor is necessary for proper brake functioning.

It is also very important to make sure that the wheel flange behind the rotor is free of any rust or debris. Failure to eliminate rust or debris will cause rotor “runout,” which, over time, will cause friction material to be transferred to the rotor surface.

6) Caliper Inspection

It should also be noted that the poor condition of a caliper may not be outwardly visible. Corrosion of the inner surfaces of the caliper from water-bearing brake fluid can cause it to bind, a “lazy caliper” condition. In cases such as this, it may be advisable to replace the caliper with a bare unit, or a semi-loaded option, which saves time and provides the assurance of a well-functioning unit.

For the counterperson, the sheer number of brake jobs you supply parts for is staggering; and considering this, the number of problems that do crop up is quite small.

However, by advising customers to redouble their efforts to pay attention to details and avoid shortcuts, especially when busi-ness ramps up and the pressure is on, it will pay dividends for them and you in fewer comebacks and a professional reputation.

Information from a variety of sources was used in creating this article, including the Affinia Group, Federal-Mogul, Fenwick Automotive, and Honeywell Friction. Special thanks to Pierre Lalonde, technical support specialist, Affinia Group Canada.

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