The Toyota Vellfire 20 series (ANH20) brake booster is a critical component in the braking system, designed to assist the driver by reducing the amount of force needed to apply the brakes.

Brake Booster Description (Toyota Vellfire ANH20):

Type:

Vacuum brake booster (also called a vacuum servo).

Function:

The brake booster uses vacuum pressure (typically from the engine intake manifold) to multiply the force applied by the driver on the brake pedal. This makes braking easier and more effective, especially in a heavy vehicle like the Vellfire.

Key Features:

• Location: Mounted between the brake pedal and the master cylinder, on the driver side of the engine bay firewall.
• Vacuum Source: Connected to the engine via a vacuum hose. For some models with hybrid or low-vacuum engines, an auxiliary vacuum pump may be present.
• Construction: A diaphragm-based unit that uses vacuum on one side and atmospheric pressure on the other to create the assistive force.
• Dual Diaphragm (common in minivans): Many Vellfires use a dual-diaphragm design to provide extra assistance due to the vehicle’s weight.

Symptoms of a Failing Brake Booster:

• Hard brake pedal.
• Increased stopping distance.
• Hissing noise when pressing the brake.
• Engine stalling when brakes are applied (due to a vacuum leak).

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