Modern Tire Dealer

APR 2019

Magazine for the professional tire industry

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Page 31 of 85

M T D A p r i l 2 0 1 9 30 B r a k e s B rake system service has its own set of issues, starting with "rust never sleeps." Especially in areas of the country that experience winter conditions, where ice-melting chemicals are applied to the roadways, closely inspect all brake lines at every opportunity (whenever a vehicle is on a li). Some of today's salt/ brine road coatings are extremely corrosive and tend to stick to undercarriages, and are difficult to wash off. Any brake line that is even marginally suspect should be replaced. Explain to the customer the need for such replacement and the necessity for catching the problem before it gets worse. A rotted brake line is compromised in terms of tubing wall thickness and resistance to brake system pressure. A compromised brake line obviously can result in a leak- age that will, sooner or later, result in a no-brake condition. Invest in a high quality brake line flaring tool. Inexpensive flaring tools can prove finicky, oen resulting in off-center flares that will not seal correctly. Also, always use a proper line wrench when servicing brake line fittings/connections. A line wrench captures more surface area along the fitting hex, eliminating the potential for damaging/rounding-off the hex. LEAKS WITH NEW LINES If you happen to deal with stainless steel brake lines, it's not uncommon to experi- ence a small initial fluid leak when a new stainless line is installed. If this occurs, loosen the connection and re-tighten. is oen corrects the issue. Stainless lines/ flares are relatively hard and sometimes require repeated cycles of loosening and tightening in order to obtain a leak-proof seating at the flare. Brake calipers that feature a banjo bolt to secure the flexible brake hose to the caliper require a crush washer on both sides of the bolt (between the bolt head and caliper and between the brake hose fitting and bolt head). Never re-use crush washers. Always install new crush washers. ese so-metal compressible washers are commonly made of copper or aluminum and are intended as one-time-use washers. As with stainless lines, new crush washers sometimes require a loosening and re- tightening in order to establish a fluid seal. BRAKE BLEEDING Air inside the hydraulic system causes a mushy pedal (or loss of pedal, depend- ing on the amount of air in the system). Remember, you can compress air, but you can't compress fluid. A regular schedule of bleeding provides two benefits: it provides an opportunity to remove any air that has been sucked into the system during use, and it gives you a perfect chance to freshen the brake fluid. Glycol brake fluid is hygroscopic, which means that it sucks up water like a magnet grabs grinding dust from your workbench. As little as a 3% moisture content can cut the brake fluid's boiling point in half ! Brake fluid, even the best and most expensive fluid, will NOT last forever. is is a consumable product, and should be changed on a routine basis. Vehicles equipped with an anti-lock braking system (ABS) require special attention when bleeding the system. If you attempt to flush and refill in the "normal" manner, you may end up with a so brake pedal. Why? Because you haven't flushed the separate passages in the module for solenoid activation. You may need to use a scan tool to cycle the system. Always refer to the service manual for specific brake system bleeding steps. Improper bleeding procedures can also cause damage to a previously good master cylinder. If a master cylinder has been operating correctly for many miles of use, and the system is then bled in the course of a normal brake job, the master cylinder's piston seals can be damaged if the pedal is pushed fully to the floor during bleeding. Over the course of long-term use, the piston inside the master cylinder travels a relatively short distance. If the system was poorly maintained and the brake fluid has absorbed excess moisture, the end of the piston bore may feature corrosion build- up in the end of the bore that normally never experiences piston travel. If, during the bleeding process, the pedal is pushed all the way to the floor, the piston is now pushed into the corroded area, possibly damaging the seal. To avoid this during a bleeding job, you can place an obstacle, such as a block of wood, under the pedal to avoid over-traveling the piston. Whenever servicing a vehicle's brake system, examine the fluid in the reservoir. If it appears dirty, vacuum the fluid out of the reservoirs and replace with fresh fluid prior to bleeding. is reduces the risk of c o m e b a c k s A FEW COMMON FIXES TO CREATE SATISFIED CUSTOMERS Mike Mavrigian By Rather than attempting to rebuild worn/ failed/sticking calipers, replace with new or remanufactured. Often loaded calipers are available that include pads, but depending on the vehicle applica- tion, severe duty pads may be required in the case of towing, heavy-duty or emergency vehicle applications.

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