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Hello IS community, this is another rookie question. What does the brake booster do and i heard it runs out. Can anyone help me on how to replace it or what I need to do to maintain that part, and is it crucial? Thank you IS community.
 

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Hello IS community, this is another rookie question. What does the brake booster do and i heard it runs out. Can anyone help me on how to replace it or what I need to do to maintain that part, and is it crucial? Thank you IS community.
a short and simple answer is this, the brake booster uses vacuum produced from your engine to help assist you with your brakes. it helps move the brake pedal in turn pushing the piston in your master cylinder; which pushing brake fluid into the calipers to move the pads towards the rotors making the car stop. flew!
there is no need to maintain it. usually the only time that it fails is when you have a leak at the master cylinder and that fluid leaks into the booster distorting the diaphragm.
the air supply in the booster will run out if the source vacuum is no longer present ie: engine shuts off. you'll notice how the pedal feels with the engine running and when the engine off.
is there an issue your having with yours?

newer lexus models have electric brakes. they use a stroke simulator to make the pedal "feel" like a normal car. pretty cool stuff.
 

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i have brake issues too please help!!

I have a question please??? I cranked up my IS after hiking one day and when I went to use the brakes the pedal didn't feel responsive like normal and the car took waaay longer to stop. Fluid level was between max and min. Pads are good. Took it to one mech and he had me do the following brake booster check. Turn the car off pump the brakes then crank the car and the pedal went down. Then while car running had me hold the brake, give it gas and the brake pedal moved up. Then went to another mech and he had me pump the brakes while car was running and we heard what sounded like a hiss from the engine bay when I would press the pedal over and over. Thinking I had a vacuum leak in a hose going to the booster. But then said he was convinced it was a vacuum check valve. Does any of this make sense to anyone??? I personally was going to begin with bleeding the brakes first to ensure no air had been intrigued into the system. Which brings me to my last cry for help. Can or how would air just get into the system when no recent brake work was done, no fluid leaking anywhere, unless and tell me if this makes sense ..... Right before my problem started I was driving and braking on a pretty rough mountain road which had the car vibrating and also with an incline and with the fluid being not at max could air be introduced into the system from the master cylinder??? I figure it couldn't hurt to bleed/flush my fluid to see if the air theory is true or do u guys think its the master cylinder or the brake booster or the said check valve??? Please advise !!!! THANKS IN ADVANCE!!!!!
 
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