The following information is copied from the service manual.
POWERMASTER BRAKES DIAGNOSTIC INFORMATION #93-5-107 - (03/31/1993)
SUBJECT: POWERMASTER BRAKES (DIAGNOSTIC INFORMATION/INSTALL NEW KIT)
VEHICLES AFFECTED: 1986 "B" MODEL (WAGONS) AND 1985-87 "G" MODEL (TURBO CARS)
THIS BULLETIN SUPERSEDES AND REPLACES CORPORATE BULLETIN REFERENCE NUMBER 035002.** THIS BULLETIN IS BEING REVISED TO INCLUDE MORE DIAGNOSTICS AND INTRODUCES NEW REPAIR KITS FOR REBUILDING THE POWERMASTER UNIT.
This bulletin provides brake diagnostic information that will help to correctly diagnose and resolve concerns with the Powermaster Brake System on 1986 "B" Station Wagons and Buick "G" 1985-87 Regal Turbo vehicles.
If, after following this procedure a technician still has a question, Delco Chassis Division has set up an 800 number for additional assistance. Call: 1-800-523-0203
CONDITION:
--------- Some owners of 1986 "B" station wagons or 1985-87 Buick Regal Turbo vehicles equipped with the Powermaster Brake System may experience either "harder pedal feel" or "increased pedal travel". The red brake warning light may also be illuminated. This should normally coincide with the hard pedal feel or warn of impending hard pedal if a concern is not resolved. It may also momentarily or continuously illuminate in conjunction with the increase pedal travel problem.
CAUSE:
----- A. "Harder Pedal Feel" symptoms can be diagnosed from this bulletin. There are four likely causes to be aware of:
1. ACCUMULATOR WITH LOW GAS CHARGE: Symptoms - Pedal is momentarily hard and/or brake warning light flickers on normal to fast brake applies.
2. PRESSURE SWITCH FAILURE: Symptoms - Pedal remains hard on all applies and pump fails to run.
3. PUMP FAILURE: Symptoms - Pedal remains hard on all applies and pump fails to run or may run continuously (with or without brake application).
4. INTERNAL OR EXTERNAL LEAKAGE: Symptoms - Pedal remains hard on most or all applies. Brake fluid may be present on outside or rear of unit. Pump runs continuously or cycles frequently (with or without brake application).
B. "INCREASED PEDAL TRAVEL" symptoms can be diagnosed from this bulletin. If this symptom is recognized in conjunction with "HARDER PEDAL FEEL", follow the diagnostic procedures for "harder pedal feel".
NOTE: Replacement of the complete Powermaster assembly is not required to correct most customer concerns. Part kits are available that will resolve most concerns with this system, and eliminate unnecessary replacement of the complete Powermaster assembly.
See Figures 1 and 2 for component identification.
HARDER PEDAL FEEL DIAGNOSTICS PROCEDURE
PROCEDURE/TEST RESULT CORRECTIVE ACTION -------------- ------ ----------------- Fluid Level/External Leakage:
Make 10 brake applies with Below minimum mark Follow Corrective Action ignition "off". Step #1. Check fluid level of pump reservoir (Fig. 2).
- OR - Above gage marks Reservoir overfilled Remove excess fluid Continue diagnostic
- OR - Within normal level No action required gage marks Continue diagnostics
WARNING
Light Operation:
Check red brake warning Light does not No action required light with normal braking illuminate Continue diagnostics (Ignition "On").
- OR - Light comes on and See accumulator operation goes off diagnostics
- OR - Light comes on and See booster operation may stay on diagnostics.
Make a series of rapid Light comes on and No action required. brake applies (one apply goes off Normal operation. per second). Continue diagnostics
Accumulator Operation:
Make 10 brake applies with 0-1 second Replace accumulator P/N ignition "off" 18014978 or 18018722 Turn ignition "on". per instructions on Check time from motor "start" installation. to red light off.
- OR - 2-7 seconds No action required. Continue diagnostics.
- OR - 8 seconds or greater Follow Corrective Action Step #2.
Booster Motor Operation:
Turn ignition on and make Motor does not run, Follow Corrective Action normal brake applies no power assist, Step #3. red warning light illuminates.
- OR - Motor does not shut Follow Corrective Action off within 15 Step #4. seconds.
Internal Leakage:
Wait for pump to shut off Pump cycle without Follow Corrective Action after normal run cycle a brake application Step #2.B Keep ignition "on" being made. Wait for five minutes.
INCREASED PEDAL TRAVEL DIAGNOSTICS PROCEDURE
(ALL MODELS)
Inspect for external leaks Leakage observed Repair leak or replace between master cylinder leaking part. Add fluid outlets and wheel brakes to master cylinder reservoir per Figure 2.
- OR - No leakage observed. Proceed to next step below.
(1986 STATION WAGONS ONLY)
Bleed left front caliper only. Pedal Travel Replace combination significantly valve with brass valve improves.* (P/N 25509419) and re- bleed total system
- OR - Pedal travel is Bleed total system and still excessive* check drum brake ad- justment.
Bleed entire brake system Pedal travel is Repair Powermaster unit and check drum brake still excessive* with Seal Repair Kit adjustment 18020067
(1985 - 1987 BUICK REGAL TURBO ONLY)
Bleed entire brake system Pedal travel is Repair Powermaster unit and check drum brake still excessive* with Seal Repair Kit adjustment. 18020067.
* Note: To properly evaluate pedal travel, apply brakes with vehicle parked, ignition off, and without power assist (de-pressurize system with ten brake applies). Pedal travel on the vehicles should be maximum of 57 mm (2-1/4 inch) with normally worn brake linings when checked at 100 pound pedal force using J-28662.
CORRECTIVE ACTION STEPS
STEP #1 - LOW FLUID IN BOOSTER PUMP RESERVOIR DUE TO EXTERNAL LEAK. ------------------------------------------------------------------ A. Make ten medium to high effort brake applies with ignition off to de-pressurize the system. Check fluid level in booster pump reservoir by observing if level falls between the two gage marks located on the inside of the pump reservoir (Figure 2).
RL
