Brakes - Pedal Pulsation/Vibration When Braking

46 08 06

Oct. 29, 2008

2015173 Supersedes T.B. Group 46 number 07-05 dated Oct. 12, 2007 due to removal of Routan applicability.





Vehicle Information

Condition

Brake Disc, Pulsation

When applying brakes at highway speeds the following symptoms may occur:

Brake pedal may pulsate

Vibration may be felt in vehicle body

Steering wheel may shake

Technical Background

For brake vibration / pulsation concerns, brake disc machining is now allowed between 6 months / 6000 miles and 12 months / 12,000 miles of the warranty in service date.

NOTE:
Vehicles between 0 and 6 months / 6000 miles in service are not eligible for brake disc machining. For braking vibration complaints on these vehicles, see Technical Bulletin subject matter Customer States "Vibration When Braking", instance number 2010245.

Vehicles after 12 months / 12,000 miles in service are not eligible for brake disc machining. For brake vibration complaints on these vehicles the brake discs may be replaced if the lateral run out exceeds 0.1 mm

Production Solution

No production change required.

Service

NOTE:
BEFORE machining brake discs, the technician must record the beginning thickness measurement on the back of the repair order followed by the ending thickness measurement upon completion of machining process. All policies and procedures outlined in this technical bulletin also apply to sublet brake disc machining.

Improperly machined brake discs may cause brake pulsation after several months in service.

The servicing facility will be responsible for failures described above.

Procedure:

^ Remove wheels and separate brake calipers from carrier as outlined in Repair Manual Group 44 - Wheels, Tires, Vehicle Alignment and Group 46 - Brakes - Mechanical components in ElsaWeb.

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)

^ Visible cracks

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.

^ Measure the brake disc thickness in 4 locations using either the Pro Cut International" disc thickness measuring tool Part No. 50-902 or the Hunter Engineering Company disc thickness measuring tool Part No. 25-99-2. Measurements MUST be taken the same distance from the brake disc outer circumference to ensure consistency.





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). Recommended on-car brake lathes are either the PRO-CUT International(TM) PFM 9.0, or the Hunter Engineering Company model OCL 400. This design of brake lathe will produce a surface quality which will provide proper brake performance without a brake pad to brake disc break-in period.

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.





^ Re-measure brake disc thickness in 4 locations using either the Pro Cut disc thickness measuring tool Part No. 50-902 or the Hunter disc thickness measuring tool Part No. 25-99-2, 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.

NOTE:
Always replace brake discs in pairs (front axle and/or back axle).





^ Measure brake disc lateral run out using Pro Cut Disc Lateral run out measuring kit Part No. 50- 700FC or the Hunter Disc Lateral run out measuring kit Part No. 25-128-2 with a dial indicator.
- Run out must not exceed 0.1 mm.





Warranty





Required Parts and Tools

No Special Parts required.

Additional Information

All part and service references provided in this Technical Bulletin are subject to change and/or removal. Always check with your Parts Dept. and Repair Manuals for the latest information.