Mercedes Benz S-Class W221 rear brake disc pump refers to the rear brake caliper pump (rear brake hydraulic piston assembly) that works together with the disc rotor and brake pads to provide braking power.

Description:

• Model: Mercedes Benz S-Class W221 (2006–2013)
• Part: Rear brake disc pump (rear brake caliper with piston)
• Function: Hydraulic caliper assembly that applies pressure to the rear brake pads against the disc rotor when the brake pedal is pressed, ensuring stopping power and stability.
• Type: Single-piston floating caliper (standard), with options for larger multi-piston calipers on AMG models.
• Material: High-strength aluminum alloy (lightweight and durable).
• Integrated with: Rear electronic parking brake motor (on some variants).
• Works with: Rear brake disc rotor, pads, ABS/ESP hydraulic system.

👉 Would you like me to make the description general (for normal W221) or specific to AMG (performance model)?