'98 Buick Regal Brake Line Failure, One Side Of Master Cylinder Won't Pump

Hello Iris, Found this information from aa1car.com. I'm only posting this here for easier reading to answer the question. Though I'd go to there site they have a lot of auto related information.

"DELCO ABS-VI BLEEDING PROCEDURE
Introduced in 1991 as an option on Saturn, Buick Skylark, Oldsmobile Cutlass Calais and Pontiac Grand Am models, the Delco ABS-VI anti-lock brake system has been used on a wide range of General Motors front-wheel-drive vehicles, including Chevrolet Lumina and APV, Chevrolet Beretta, Corsica and Cavalier, Pontiac Grand Prix, Sunbird, Oldsmobile Cutlass Supreme and Buick Regal.

The Delco VI system is a nonintegral ABS system with a conventional master brake cylinder and power booster. It has four wheel-speed sensors, but is a three-channel system. The front brakes are controlled separately, but the rear brakes share a common ABS circuit. Attached to the master cylinder is the hydraulic modulator and motor pack assembly. The modulator is held by two banjo bolts at the master cylinder�s two upper outlet ports, and two transfer tubes at the two lower outlet ports. An important service point to note here is that the two lower transfer tubes and O-rings must be replaced if the master cylinder and modulator are disconnected from one another. This is necessary to prevent leaks that could cause the brakes to fail.

The modulator assembly has fluid chambers for all four brakes, two isolation solenoid valves, four check balls, a motor pack containing three bidirectional direct current motors with electromagnetic brakes (EMBs) and/or expansion spring brakes (ESBs), three ball screw assemblies, four pistons, a gear drive set and gear cover. The modulator motor pack, isolation solenoid valves, gear cover and individual gears are all serviceable parts and can be replaced separately.

The brakes on GM cars equipped with Delco ABS-VI may be bled using manual, vacuum or pressure bleeding. The usual bleeding sequence is right rear, left rear, right front, left front.

Before you begin, however, you must make sure the rear pistons in the Delco ABS-VI modulator are in the home position so the check balls are unseated. If this is not done, you won't be able to bleed the rear brake lines. There are two ways that this can be accomplished: With the Tech 1 or similar scan tool, select the F4 ABS Test mode, then select the F0 manual control option. You can now command the rear motor to drive the pistons to the home position.

Without a scan tool, open the front bleeder screw at the modulator. There are two, so be sure you open the front one. Then bleed the modulator. Close the screw, then bleed both front brakes starting with the right one first. After checking for a firm pedal, drive the vehicle above three miles per hour. The controller will automatically reset the system by commanding the rear motor to run to the home position. Once this has occurred, you can stop the vehicle and bleed the rear brakes."

This should help.

Charles