Remove the master cylinder

Fig 1: Removing/Installing Master Cylinder

Courtesy of VOLVO CARS OF NORTH AMERICA.

Avoid brake fluid spillage when removing.

Remove the soundproofing panel and the power brake booster 

For the soundproofing panel, see Remove the driver's side soundproofing panel

Fig 2: Nuts Securing Power Brake Booster To Firewall

Courtesy of VOLVO CARS OF NORTH AMERICA.

Remove: 

• the retaining clip for the push rod for the power brake booster
• the four nuts securing the power brake booster to the firewall.