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BoppinAbout
Novice
Apr 18, 2010, 10:03 AM
Post #1 of 10
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Brake pedal sinking
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97 Corolla, 167K miles.
After a poor emergency stop two weeks ago I found my break lines were leaking and had them replaced. Car now stops fine---even with a hard stop---but the pedal slowly sinks about halfway down when stopped at a light. I wasn't having this problem---or at least, I wasn't aware of it---prior to having the brake lines changed.
There has been no loss of braking power or of brake fluid in the last two weeks. Mechanic checked the lines again and they are not leaking. I believe he properly bled the lines (I was there and helped him do it, so I know the pedal was firm after bleeding).
My understanding is that the most likely cause of the sinking pedal is an internal leak in the master cylinder.
2 questions:
1) How urgent is this problem? If the car is stopping ok, should I be ok driving around town for a day or two to buy the parts and get to my mechanic? Or do I need to stop driving immediately?
2) Should I just go ahead and change the master cylinder, or should I ask the mechanic to check the wheel cylinders, calipers, and anything else related? If it's most likely the master cylinder, might it be cheaper to start with that??
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 18, 2010, 10:09 AM
Post #2 of 10
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Re: Brake pedal sinking
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That is a very urgent problem. You won't have a brake pedal when you need it most and won't have time to pump it up.
There is a good chance you are right about the master cylinder but it could also be the ABS unit although the only way to find out is replace the master, assuming you are not losing any brake fluid.
Losing a master cylinder after another brake failure is not an unusual thing to happen. When you were bleeding and when you had the initial failure, the master cylinder pedal pushed the seals further down into the bore than they normally travel and this are is commonly full of junk and corrosion, tearing or damaging the seals as they pass by.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Apr 18, 2010, 10:09 AM)
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BoppinAbout
Novice
Apr 18, 2010, 10:18 AM
Post #3 of 10
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Re: Brake pedal sinking
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Thanks very much for that explanation of how the emergency stop both blew out the brake lines and damaged the master cylinder. It makes sense.
My 97 Corolla doesn't have antilock brakes to my knowledge.
Clarification: When stopped at a light, I do NOT have to pump the brake to prevent the car from creeping forward. The brakes hold the car fine. All stops seem to have full power. Given that, is it ok to drive to the parts store and to my mechanic? Total distance is only a few miles of low-speed driving.
I would describe this pedal sinking problem as mild, not severe. It is barely noticeable. However, I do take it seriously and will attend to it tomorrow, don't worry. Just need to know if I can drive to the parts store.
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 18, 2010, 11:31 AM
Post #4 of 10
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Re: Brake pedal sinking
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I understand exactly what is happening and although it may not seem like much, if you do any long braking as coming off an interstate, you could have nothing when you get to the end. Giving it a pump will bring the pedal back but you may not have time for that. It could suddenly get worse also.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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BoppinAbout
Novice
Apr 18, 2010, 11:33 AM
Post #5 of 10
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Re: Brake pedal sinking
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OK, thanks, I will take care of it immediately. No interstate driving.
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BoppinAbout
Novice
Apr 18, 2010, 1:14 PM
Post #7 of 10
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Re: Brake pedal sinking
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I fully understand, but I have to at least get the car to my mechanic. The auto parts store and the mechanic are both about 2 miles from my house. The mechanic tested the brakes and said he felt the problem wasn't urgent. I just wanted to doublecheck with you folks. I will take care of this tomorrow.
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Sidom
Veteran
/ Moderator
Apr 18, 2010, 1:20 PM
Post #9 of 10
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Re: Brake pedal sinking
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Well I do feel better now, knowing that you aren't planning on driving it for a few days like it sounded like you were planning....Thank you
Be extremely careful driving it even to the shop, be aware of the park brk in case needed.....When a panic situation arises, everything starts going 100 miles an hour and you have very little time to react. Remember your emergency stop earlier and how fast everything seemed to happen at the time.......
Sometimes a cheap tow might not seem like a bad idea.....
Good luck with your problem and hope it gets fixed quick for you.
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BoppinAbout
Novice
Apr 18, 2010, 1:55 PM
Post #10 of 10
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Re: Brake pedal sinking
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Maybe I exaggerated the amount of sinking. Definitely not to the floor, nor quickly. It took me a few days to even realize it was happening.
I trust this mechanic. He's done a lot of work on my car and seems more skilled than any mechanic I've had in the past. But I'm a cautious person and will take care of this right away.
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