GM Service Manual Online
For 1990-2009 cars only

The entire hydraulic brake system should be thoroughly flushed with clean brake fluid if there is any doubt as to the grade of the fluid in the system or if the fluid used contains the slightest trace of mineral oil.

All rubber parts which have been subjected to contaminated fluid must be replaced before flushing the system.

Flushing is performed at each wheel similarly to bleeding. The new fluid must be forced through the system until it emerges clear in color. Approximately one quart of new fluid is needed to flush the system.

After completing the flushing operation at all of the bleeder valves check that the master cylinder is filled to the correct level.