CAMPAIGN:BRAKE MASTER CYLINDER DAMAGED CENTER VALVE

MODELS: 1986 CORVETTE

DEFECT INVOLVED:

General Motors of Canada has determined that a defect which relates to motor vehicle safety exists in certain 1986 Corvettes. Certain severe and unusual braking conditions may cause damage to the brake master cylinder centre valve. If sufficient damage accumulates, loss of front brakes may occur with accompanying increased pedal travel and reduced braking ability. A reduction of braking ability at a time when minimum stopping distance is required could result in a vehicle crash without prior warning.

To prevent passibility of this condition occurring, Dealers are to install a brake master cylinder piston kit on all involved vehicles in accordance with instructions contained in this campaign bullet'in.

VEHICLES INVOLVED:

Involved are all 1986 Corvette Models within the following breakpoints:

PLANT FROM THROUGH

Bowling Green G51GO001 G5118892

All affected vehicles have been identified by the VIN listing provided to involved Dealers with this bulletin. Any Dealer not receiving a listing was not shipped any of the affected vehicles.

DEALER CAMPAIGN RESPONSIBILITY:

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your Dealership for service in the future, you should take the steps necessary to be sure the campaign correction has been made before reselling or releasing the vehicle.

Owners of vehicles recently sold from your new vehicle inventory are to be contacted by the Dealer, and arrangements made to make the required modification according to instructions contained in this bulletin.

CAMPAIGN PROCEDURE:

Refer to Section 4 of the Service Policies and Procedures Manual for the detailed procedure on handling Product Campaigns. Dealers are requested to complete the campaign on all transfers as soon as possible.

OWNER NOTIFICATION:

All owners of record at the time of campaign release are shown on the attached computer listing and have been notified by first class mail from General Motors. The listings provided are for campaign activity only and should not be used for any other purpose.

PARTS INFORMATION:

Parts required for this campaign should be ordered through regular channels, as follows:

PART NO. DESCRIPTION QUANTITY/VEHICLE

10052271 Master Cylinder Piston Kit 1

PARTS AND LABOUR CLAIM INFORMATION:

Credit for the campaign work performed will be paid upon receipt of a properly completed campaign claim card or RAPID terminal transmission in accordance with the following:

Repair Code Operation Time Allowance

2A Install Master Cylinder 1.5 Piston Kit

Time allowance includes 0.1 hour for Dealer administrative detail associated with this campaign. Parts credit will be based on Dealer net plus 30% to cover parts handling. An amount of $5.28 will also be paid for brake fluid.

SERVICE PROCEDURE

Disassembly

1. Remove master cylinder from vehicle.

2. Drain and discard brake fluid from master cylinder reservoir and bore.

3. Fully depress the master cylinder pistons with a brass rod or wooden dowel (28) (as shown in Fig. 1) and remove stop bolt (9). Then remove snap ring (1) with suitable Truarc pliers.

Do not remove stop bolt (9) unless both pistons are fully bottomed in bore.

4. Remove brass rod or wooden dowel (28) and gently bump open end of master cylinder body on a piece of wood to remove primary piston (3) secondary piston assembly (7) and centre valve assembly(B).

5. Discard secondary piston assembly and centre valve assembly (7&8).

6. Remove primary piston seal retainer (6) by carefiilly prying open the legs of the seal retainer with a small screwdriver. Discard the retainer.

7. Remove and discard the primary piston seals (2 & 5). Do not dismantle any other part of the master cylinder.

Installation

1. Lubricate new secondary seal (2) with clean brake fluid and install on primary piston with seal lip facing as shown (Fig. 2).

2. Insure recuperating guide (4) is located on primary piston as shown (Fig. 2).

3. Lubricate new main seal (5) with clean brake fluid and install on primary piston (3) with lip facing as shown (Fig. 2).

4. Press new seal retainer (6) onto primary piston (3) make sure retainer tabs snap into piston groove.

5. Flush bore of master cylinder with fresh clean brake fluid, drain and discard excess fluid.

6. Insert new centre valve assembly (8) into secondary piston assembly (7), then install in cylinder bore.

7. Install primary piston assembly (3) in cylinder bore.

8. Using brass rod or wooden dowel (28), push the primary piston (3) down the cylinder bore until both primary and secondary pistons bottom in cylinder bore. Then install stop bolt (9) and torque to 9-12 N.m (7-9 lb. ft.).

Do not install stop bolt (9) unless both Distons (3 & 7) are fully bottomed in bore.

9. Install snap ring (1) in the master cylinder bore making sure it fits into the groove properly. Remove brass rod or wooden dowel (28).

10. Fit plastic tie wrap identification tag around body of master cylinder adjacent to stop bolt to show that cylinder has been reworked.

11. Reinstall cylinder on vehicle, torque attaching nuts to 20-34 N.m. (15-25 lb. ft.), bleed brake system and top off fluid reservoir.

12. Reconnect warning switch electrical connection.

13. Install Campaign Completion Label.

INSTALLATION OF CAMPAIGN IDENTIFICATION LABEL

Clean surface of radiator upper mounting panel and apply a Campaign Identification Label. Make sure the correct campaign number is inserted on the label. This will ijidicate that the campaign has been completed.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.