Ed Dorowski, ALLDATA Editor Jeff Webster, ALLDATA Technical Writer
Diagnosing a repair can be challenging. In the case of a manufacturing defect, a solution can be especially elusive. For any diagnosis – difficult or relatively simple — manufacturers’ repair information is the solution for timely and profitable repairs.
Technical service bulletins (TSBs) may expedite repairs because they describe known problems and the procedures for fixing them. It’s always a good idea to search for a TSB first. You’ll often save time. Here, for example, is a TSB from Volkswagen® that describes a known issue with the brakes on most models:
Volkswagen drivers may complain of a pulsating brake pedal when applying the brakes at highway speeds. The pulsation may also be felt as a vibration in the vehicle body. Additionally, the steering wheel may shake. The cause may be improperly machined brakes, and the condition may not be felt until several months after the brakes were machined. To correct the problem, follow the steps in this Tech Tip.
Review safety procedures in ALLDATA Repair® S3000 before beginning.
Remove wheels and separate brake calipers from carrier using factory and/or industry standard approved practices.
Brake Disc Inspection
A detailed brake disc inspection is needed to determine if the brake disc should be machined or replaced.
Inspect brake disc friction surfaces on both sides of the brake disc for:
Severe discoloration (bluing)
High heat surface damage (raised hard spots)
Brake discs showing any of the above described conditions MUST be replaced.
Disc Thickness Measuring
Each brake disc has the minimum allowed thickness cast, stamped or laser-etched into the disc hub (Figure 1).
Measure the brake disc thickness in four locations using factory and/or industry standard approved practices. Measurements MUST be taken the same distance from the brake disc outer circumference to ensure consistency (Figure 2).
NOTE: The brake disc must exceed the minimum thickness after the machining process is completed in order to be reused.
Brake Disc Machining
Tip: Brake discs must be machined in pairs (front axle and / or rear axle).
NOTE: To ensure that a high quality brake disc finish is produced, brake lathe cutting tools must be maintained as directed by the lathe manufacturer.
Follow the brake lathe manufacturer’s instructions for set-up and machining.
Wash the brake disc with a soap and water solution upon completion of resurfacing to remove all machining particles (Figure 3).
Re-measure brake disc thickness in 4 locations to verify that minimum thickness is still exceeded. If recorded brake disc measurement is less than the minimum thickness, the brake disc MUST be replaced (Figure 4).
NOTE: Always replace brake discs in pairs (front axle and/or back axle).
Measure brake disc lateral run out. Run out must not exceed 0.1 mm (Figure 5).
Drive the vehicle to verify the repair.
NOTE: This Repair/Service Procedure is excerpted from a Technical Service Bulletin published by the vehicle manufacturer, and is intended for use by trained, professional technicians with the knowledge, tools and equipment to do the job properly and safely. It is recommended that this procedure not be performed by “do-it-yourselfers.”
Ed Dorowski has 19 years of Domestic and Import dealership and independent shop experience as a service consultant, ASE Certified Master Technician, Nissan® Certified Master Technician, & California Smog Test & Repair Technician.
Volkswagen, VW and Routan are registered trademark names and model designations of Volkswagen of America, Inc. Nissan is a registered trademark of Nissan Motor Co. Ltd. All trademark names and model designations are being used solely for reference and application purposes.