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
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
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
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
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
Wash the brake disc with a soap and water solution upon
completion of resurfacing to remove all machining particles
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