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Q: brake booster and master cylinder

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i replaced the power brake booster and master cylinder bled the brakes but the brake pedal dosent retract all the way.
My car has an automatic transmission.

A: Your first step is to verify that the parts...

Your first step is to verify that the parts you purchased are EXACTLY like the ones you removed. It is possible to have a a similar component fit but have the wrong clearance for the brake pedal pushrod. If they appear to be the same, remove the master cylinder to verify that the plunger is retracting fully. If it is not fully retracting within the master cylinder, return the part and get a new one.

It is also possible that the booster has a different internal design causing the pedal pushrod to have too much free play. Finally, check that the brake pedal return spring is correct and functioning. Sometimes lubricating the brake pedal where it pivots will help. Refer to the factory service manual for exact measurements and specifications of the brake system components. If you’re still in need of help, a certified technician, like one from YourMechanic, will be able to properly test and diagnose your brake pedal concern if needed.

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A: The brake booster pin in the brake booster ...

The brake booster pin in the brake booster is what actually inserts into the back of the master cylinder. Some older cars have an adjustable pin or may have more than one position. If you did not have this problem before replacing the booster and master cylinder, it’s possible that the pin is maladjusted or possibly the wrong pin. If you still have the old booster, you may want to compare the two pins to verify. If you need an expert to check this out in person, a mobile mechanic from YourMechanic can come to your car’s location to diagnose your brake pedal issue and help you move forward with repairs.

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