Warranty - Reducing Disc Brake Comebacks
9231pontiac01
Bulletin Number: 92-5-16
Reference Number: 235005R
Publish Date: 6/92
Subject:
REDUCING DISC BRAKE COMEBACKS (NEW TOOL KIT AND POLICY CHANGE)
Models Affected:
1992 FIREBIRD, BONNEVILLE, SUNBIRD GRAND AM, LEMANS, GRAND PRIX AND TRANS SPORT MODELS
POLICY CHANGE:
As of June 1, 1992 the add operation B (reface disc) on labor codes H0042, H0043, H0120, H0121 H0127, H0130, H0131 and H0137 will NOT be paid.
EXPLANATION OF POLICY CHANGE
It has been found that:
1. Rotor refacing is often done inaccurately resulting in increased comebacks.
2. Rotor refacing during normal pad replacement is not necessary.
3. Rotor refacing for cosmetic corrosion on new vehicles is also unnecessary. Clean-up of braking surfaces can be accomplished by 10-15 moderate stops from 35-40 mph.
4. Rotor refacing can often result in loss of brake effectiveness.
5. Rotor refacing is also ineffective in correcting BRAKE SQUEAL, HIGH PEDAL EFFORT and/or PREMATURE LINING WEAR OUT, and should not be used to address these conditions.
6. When installing new rotors, it is unnecessary to reface the new rotors. Just a clean-up the braking surfaces with "Brake Kleen" or equivalent is sufficient.
Additional brake information will be obtained by Delco Chassis from studying/inspecting the rotors returned under this new policy. PLEASE RETURN ROTORS PER CORPORATE PARTS RETURN PROGRAM TO:
DELCO CHASSIS DIVISION - GMC
1435 CINCINNATI STREET
DOCK #4 - PP - C76
DAYTON, OH 45408-2668
SUGGESTED BRAKE SERVICE TECHNIQUES
PULSATION:
Caused by improper rotor turning, normal wear, extreme surface rust and improper torquing of wheel nuts. Initially, determine the front vs. rear brake pulsation location using the service manual. (The following comments refer to front disc brake pulsation problems.)
Excessive lateral runout on brake rotors may be caused by distortion of the braking surface due to incorrect wheel nut torque or improper tightening sequence. Index the wheels for correct repositioning. Remove the two front wheels and inspect the rotor/wheel interface for debris or rust and clean the mating surfaces. Then retorque the wheel nuts in the STAR PATTERN sequence using the appropriate Torque Stick. Road test the vehicle. If the pulsation is not corrected, replace the rotors.
NOTE:
To help reduce pulsation and assure correct retorquing of wheel nuts, Pontiac Division is releasing (June 1) a required tool kit (Kent-Moore P/N J39544) that is designed to limit wheel nut torque levels if an impact wrench is used for wheel installation. This tool (sometimes called a Torque Stick) is not applicable to LeMans. Any time this special tool is not available, a torque wrench MUST be used.
Use Labor Operation:
T3261 Wheel Removal and Torquing To Correct Pulsation (Front Only)
Labor Time: .5
BRAKE NOISE:
Brake noise is caused by vibration of brake components. Some intermittent brake noise is normal. Usually 3-4 aggressive stops will temporarily reduce or eliminate most brake squeal. If this does not work, index, remove and remount the wheels and make sure wheel nuts are torqued in the STAR PATTERN to specification. If the noise persists, a brake dampening compound may be applied to the back of each pad. Use Permatex Disc Brake Quiet #126HB or equivalent.
ROTOR GROOVING:
Excessive grooving can be caused by foreign material in contact with the rotor, but most often rotor grooving is the result of normal brake wear. DO NOT REPLACE ROTORS FOR LIGHT GROOVING. Replace rotors only when grooves of .060 in. (1.5mm) or deeper are present.
NOTE:
A dime may be used to determine disc brake groove depth. Place a dime in the groove, with Roosevelt's head toward the groove. If the dime goes into the groove beyond the top of his head, the groove exceeds .060 in. and the rotor should be replaced. If the groove is too narrow for the dime to be inserted, it is not a cause for concern.
HIGH PEDAL EFFORT:
Follow service manual diagnostic procedures for this condition. Replace rotors if they have been previously turned (they may have been turned out-of-spec).
RUSTY ROTORS:
Most often rust is cosmetic and can be eliminated. Light surface rust may occur when a vehicle is not used for an extended period of time and it often disappears after a few normal driving stops. New car dealers dealing with rotor surface rust can usually burnish brake rotors clean. 15 moderate stops from 35-40 mph (with cooling time in-between) are usually sufficient.
CUSTOMER SERVICE NOTES:
Your customers should be made aware of the maintenance requirements of their Pontiac. These owner responsibilities are described and listed in the Owner's Manual under Periodic Maintenance Inspections. (Example: Brake Linings, Tire and Wheel Inspection and Rotation are owner maintenance).
PDI sheets describing wheel nut torque requirements and procedures will be updated for 1993 vehicles.
ADDITIONAL BRAKE-FACTS:
^ Brake surfaces should NOT be rough. Rotors should be as smooth as possible.
^ To ensure maximum brake performance and decreased comebacks, wheel nuts should be torqued to specification using proper tools and star pattern technique.
^ Rotors wear from normal use. Rotors do not warp.
^ New rotors should NOT be turned before installation. A cleaner may be used to clean brake surfaces.
^ Rotors with perceived hard spots or discoloration should not be turned. These conditions are not abnormal.
^ Installation of new rotors does not necessarily mean pads need replacement. Do NOT replace pads unless their condition requires it.
II. OVER TORQUING OF WHEEL NUTS:
1. A TORQUE WRENCH OR TORQUE STICK MUST BE USED to insure that the wheel nuts are tightened to specification. This should be done in 2 steps using the STAR PATTERN. First, snug the nuts down by hand. Then, using the STAR PATTERN and a torque wrench/stick, tighten the wheel nuts to about half the final torque. Finally, tighten the wheel nuts to specification using the STAR PATTERN and a torque wrench/stick.
2. NEVER use lubricants or penetrating fluids on wheel studs, nuts, or mounting surfaces. Wheel nuts, studs, and mounting surfaces must be clean and dry.