Preparation

• The brake master cylinder is at the back of the engine compartment on the driver's side. Ensure your Blazer is in park and the parking brake is set. You will need a crescent wrench and a socket wrench to complete the removal. The cylinder is held on by two bolts in the brake booster, and the brake lines run through to the side of the cylinder.
  
  

Removal

• Disconnect the brake lines running into the cylinder. Use the crescent wrench to loosen the lines. Lay something underneath the Blazer to catch the excess fluid that is in the brake lines. Once the lines are disconnected, remove the mounting bolts on the brake booster. These are held on by two nuts; unscrew the nuts with the socket wrench. The master cylinder will come loose. Pull it out with your hands, holding it at an angle, and drain the fluid into a container. Finally, to remove the reservoir from the Blazer master cylinder, pry it off with a screwdriver. Also remove the two rubber grommets sitting in the cylinder; pull them out with your fingers.