Auto body repair & detailing: scapping sound brakes


Question
QUESTION: Hello Dave you have been really helpful I notice when i press my brakes I getting very bad scraping noise I didn't know if that was from the brakes or where they repair my car It sounds kind of like a lawnmower Thank you for all your reply You have been a big help Carolyn

ANSWER: Hello Carolyn!....A scraping sound coming from a braking system, can mean a few different things. It can be possibly something as simple as just dirt embedded in the calipers and brake pads in a disc brake system, and the same thing in a drum brake system. In a lot of disc brake systems on today's vehicles, there is a "wear sensor" installed on the brake pads themself. The wear sensor is designed to make the exact sound you are describing. It is designed to alert the driver that the disc pads need to be replaced as soon as possible, and to avoid any further possible damage to the brake rotors and other components. Hopefully, this is the issue. Unfortunately, a scraping noise can also mean that the brake pads and shoes have been ground down to where they have caused damage to the rotors and drums....Either way, PLEASE get this checked out as soon as possible at your local Mechanic. This definitely a safety concern....Thanks again for your question Carolyn. You are very welcome also. Hope I have helped you out....Take care....Dave.

---------- FOLLOW-UP ----------

QUESTION: Hello Dave will I went to get my brakes inspection You were right my brakes need replace But i  have a bad master cylinder Which is very dangerous I had one before it was place In 2012 I cant beleive I need to replace it again What would cause the master cylinder to go bad so quick Will you lose break fluid And the car will not stop It scary an dangerous  And then  I started to feel the brake go to the floor and the brake felt spongy So i told them about it the Mechanic drove it and said he tried to stop at stop sign car would not stop     Will he going to place the master cylinder And reversed the rotors he said i still had some on them And then i  need to get front brakes I just don't have the money to replace them so Do you think if he replace the front brakes and master cylinder That would be ok It until I can replace brakes Thanks again for you help

Answer
Hey Carolyn!....Thanks for the update. In regards as to what would cause a new master cylinder to go bad so quickly, could be due to a few reasons. First, if a remanufactured/rebuilt one was installed, there is a good chance that the cylinder was not machined properly enough to remove all scratches and gouges. This would result in the plunger and seals not sealing properly, therefore letting the brake fluid bypass from the front reservoir to the rear, and visa versa. This will give you the exact "Spongy" condition you are referring to. Second, master cylinder failure could be the result of contaminated and dirty brake fluid also. Dirt in any hydraulic system over time, will cause the scratches and gouges in the cylinder walls, and exactly why machining   properly is critical when rebuilding one. Third, there is also the possibility of both the improper machining, and defective internal parts installed inside the unit....As for replacing the pads, rotors and master cylinder on your vehicle, the best advice I can give you, is to trust your Mechanic. As I am Licensed in the Autobody Trade, Mechanics are Licensed in the Motor Trade, which definitely includes a braking system. They are the professionals in that area, and being this is a safety issue, they will give you the proper guidance as to what needs replacing immediately, and what can be done at a later date.....Hope this helps you out Carolyn....If there is anything else I can try and help you out with, please drop me a line anytime.....All the best, and take care.....Thanks....Dave.