I am a new driver and for a couple of days when I press the brake pedal, sometimes it sinks to the floor to stop. It usually happens after driving a few miles without braking but sometimes it happens right after starting the car and moving. We replaced the brake calipers and pads and bled the air out of the lines a few times with the mechanic and he confirms that there is no problem in the master cylinder and ABS module and there is no any leak on the hoses as well. But one of the rear rotors turned a little purple and he said it could be the cause for sinking and telling me try driving the car for a couple of weeks and the problem may go away. Replacing the rotor could clearly clarify if the issue is with the rotor, but replacing everything to find the problem is so costly and I am student. Cloud it really be the rotor that causing the brake pedal sink sometimes but not always? It seems really dangerous to drive for weeks like this as you don’t know when it works properly or fails.

  • Welcome to Motor Vehicle Maintenance & Repair! What is the year/make/model/engine of the vehicle you're driving? How many miles are on the vehicle? Commented Mar 7 at 12:16
  • Presumably you had the work done because of the spongy brakes. If so, it's a bit off for the mechanic who did the work to say "maybe it will improve" when they haven't fixed the problem, and the brake performance could be a major safety issue. A worn rotor is very unlikely to cause the symptom mentioned. Commented Mar 7 at 19:38

1 Answer 1


A few possibilities. But you should never keep driving a car hoping brake problems go away. They don't and it's dangerous. There is a cause for this problem, and it can be fixed. The place to start is the blue rotor. It is overheating. The cause for this is usually sticking slides, faulty caliper or a bad brake hose not allowing the calipers to release pressure on the pads. Depending on the age and condition of the vehicle the overheating of this wheel could cause the water contaminated brake fluid to boil causing your symptoms. So first you need to resolve this wheels problems. Then when all wheels are functioning properly the system needs bled properly. This should also include an ABS bleed. With all four wheels working and all air removed with good brake fluid, the only thing that could cause this is air in your master cylinder or a faulty master cylinder. I realize that your mechanic confirmed these things were good, but frankly, a mechanic that tells you to keep driving on faulty brakes in hopes that it gets better is not trustworthy to confirm such things. You really should find another mechanic. You say you can not afford to do much, but you definitely can't afford driving without good brakes.

  • Is the slave cylinder part of the caliper on this vehicle? There has been no mention of them. Commented Mar 7 at 21:33
  • When I press the brake pedal suddenly it is holding normally but when I press slowly it is sinking all the way down even when the car not moving. And when it sinks there is a feeling that the right side brake not holding because car shakes little to sides especially right side. BTW all brakes are caliper brakes there is no drum brake
    – Mr. Sardor
    Commented Mar 8 at 7:33

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .