Service Procedure 1985-1986 Models

Service Procedure

Note: Care must be taken to prevent brake fluid from contacting any painted surface.

1985-1986 Models:

Always ensure that the brake system is operational after performing brake work and before returning the vehicle to the customer.
Steps A, B, and D involve all subject vehicles. Step C is engine dependent.

FIGURE 1 - COMBINATION VALVE:

A. Replacement of the combination valve, Figure 1.

1. Disconnect negative battery cable.
2. Disconnect the four brake lines at the combination valve.
3. Disconnect electrical harness at the combination valve.
4. Disconnect combination valve at bracket on the brake booster and discard valve.
5. Install new combination valve (P/N 15571205).
6. Reverse above procedure for reinstallation and tighten bracket nuts to 50 N-m (37 ft.lbs.).
7. Reinstall brake lines and torque nuts to 25 N-m (18 ft.lbs.).

FIGURE 2 - DRUM BRAKE COMPONENTS:

B. Replacement of the brake shoes, wheel cylinders, and link pins, Figure 2.

1. Loosen lug nuts on rear wheels.
2. Hoist vehicle and remove lug nuts and rear wheels.
3. Remove brake drum retaining clips (2).
4. Remove brake drum.
5. Remove brake shoe hold down and retainer springs.
6. Remove brake shoes and discard.
7. Disconnect brake line at wheel cylinder.
8. Remove wheel cylinder and discard.
9. Install new wheel cylinder (P/N 18004888) after inserting link pins (2) (P/N 5464748).
10. Tighten wheel cylinder bolts to 18 N-m (13 ft.lbs.).
11. Connect brake line to cylinder, torque nut to 20 N-m (14.5 ft.lbs.).
12. Install new brake shoes (P/N 12321427).
13. Adjust running clearance to .030 +/- .005" adjustment clearance.
14. Reinstall brake drum, retainer clips, and wheel.
15. Bleed brakes, refer to Astro Service Manual, pages 5-5 and 5-6.
16. Repeat on opposite wheel.

FIGURE 3 - TACHOMETER TERMINAL AT DISTRIBUTOR CAP:

1985 Model 4.3L Carbureted Engine

C. Reduce cold idle speed to 1600 rpm.

1. Remove dash extension.
2. Remove engine cover.
3. Install tachometer. The tachometer (tach) terminal is next to the engine control switch (bat) connector on the distributor cap (Reference Figure 3).
Note: The tachometer terminal must never be allowed to touch ground because damage to the module inside the distributor and/or ignition coil can result.

4. Reduce cold idle speed to 1600 rpm by adjusting the fast idle screw. Refer to tune up label for procedure.
5. Remove tachometer and reinstall engine cover and dash extension.
6. On a clean dry surface, next to the existing tune up label located on the fan shroud, place label P/N 10066488.

FIGURE 4 - PROM 4.3L 1986 M VAN:

1986 Model 4.3L TBI Engines

C. Replacement of the PROM, Figure 4.

1986 model vehicles built before VINS listed below require PROM replacement.

VIN EMISSIONS

GB203188 Federal Emissions
GB203623 California Emissions

Vehicles built after these VIN breakpoints have PROM factory installed.

Note: Any time the PROM is installed backwards and the ignition switch turned on, the PROM is destroyed and must be replaced.

1. Disconnect negative battery cable.
2. Remove kick panel from right side of the vehicle (1 screw) interior.
3. Remove ECM (2 screws).
4. Disconnect electrical harnesses from ECM module.
5. Remove ECM cover (2 screws).
6. Remove PROM from ECM and replace with new PROM, P/N 16068877 (Federal), P/N 16068926 (California).
7. Replace ECM cover.
8. Reconnect electrical harness.
9. Secure ECM module to its mounting location.
10. Replace kick panel.
1985 - 1986 2.5L TBI Engines

C. Vehicles equipped with this engine do not require PROM replacements.
D. Brake Burnish Procedure

On a dry clean level roadway, make twelve stops using the following procedure:

First Stop: Stop vehicle from 40 mph by applying the brakes to achieve a deceleration rate of 10 ft/sec/sec. (A 10 ft/sec/sec deceleration is equivalent to stopping the vehicle from 40 mph in 6 seconds.)

Second through Eleventh Stops: Stop vehicle from 50 mph by applying the brakes to achieve a deceleration rate of 15 ft/sec/sec. (A 15 ft/sec/sec deceleration is equivalent to stopping the vehicle from 50 mph in 5 seconds.)

Twelfth Stop: Stop vehicle from 40 mph by applying the brakes to achieve a deceleration rate of 10 ft/sec/sec.

In order to allow brake temperatures to stabilize, it will be necessary to drive 1/2 mile between stops without applying brakes. Following completion of burnish procedure (twelfth stop), drive vehicle 3 miles keeping brake usage to a minimum in order to achieve sufficient brake cool down.