The brake pedal in my car has become hard to press and sometimes has a mushy feel to it. I went to the dealership and they performed a full brake job on both the front and the rear. Several weeks after the brake job, the same problem occurred and the brakes became difficult to press. This time I almost hit another vehicle! Fortunately, I pulled the emergency brake in time. I returned to the dealership and now this time they tell me that the booster is out (very expensive to replace). I have not agreed to any more work yet and want to know your assessment of my car’s condition. Why didn’t the brake job work and why do they want to replace the booster?
A "normal" brake job only addresses wearing parts like brake pads and rotors (or brake shoes and drums on drum brake vehicles). The brake booster rarely fails, and then usually because the brake master cylinder has allowed brake fluid to leak on to the vacuum diaphram inside the unit, causes the diaphram to rupture. This eliminates brake pedal assistance, and often makes the engine run rough as well. The packaging of components in option-packed vehicles such as your Lexus usually results in components like the brake booster being surrounded by lots of other things - lots of labor to get to and replace. A professional mechanic, like a certified technician from YourMecanic, can make this repair for you at your home or office.