Q: Could the brake servo booster that the master cylinder attaches to cause the brake pedal's excessive travel?

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I have a Toyota avensis 2008 model. My issue is the brake pedal is traveling to the floor when brakes are applied. I have inspected the brake lines, calipers and have changed the master cylinder. But the problem has not gone. The only other option am remaining with is the brake servo booster that the master cylinder is attached to. When I step on the brake pedal a sound like of some pressure being released comes. Could this servo booster be the issue?

My car has 150000 miles.
My car has an automatic transmission.

Hi there. Typically, when a brake booster fails, the result is a hard to push brake pedal. The pressure release you hear is engine vacuum and may be normal considering, the brake pedal travels to the floor. With no apparent leak(s) in the hydraulic braking system, the master cylinder internally bypassing is the most common failure. Having replaced the master cylinder, this leads me to believe, there may be air trapped and a flush may resolve this concern. Assuming, the vehicle is equipped with ABS (anti-lock brake system). The ABS hydraulic modulator assembly may be internally bypassing. I recommend having your vehicle’s brake pedal issue diagnosed and repaired by a certified technician, such as one from YourMechanic.

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