Join the Car Talk Community!

Discussion Rules

Welcome to the Car Talk Community!

Want to ask a question or join the discussion? Great! Join now.

Sign In Register

Brake Pedal goes to floor and car won't stop, WHY?

I was driving my 94 Honda Prelude and put the brake peddle to the floor, but the car wouldn't stop. This was a onetime occurrence, but a dangerous one. So I checked the brake reservoir and it was full. I can't find any leaks. Please help me find out why this happened and how to prevent it. (Also the e brake doesn't work and so I don't know if that?s connected)


  • edited August 2010
    This is a classic symptom of a failing master cylinder. You will probably need a new one.

    Have the car towed to a shop for a proper diagnosis and repair.
  • edited August 2010
    Thank you for your reply. Does it matter that it is intermittent. It has only happened once. Also would a master cylinder failure result in faded brakes, or brakes that don't work as well as they should?
  • edited August 2010
    It might only happen just once more, right at the end of your life or the life of someone who was in front of you. If you did survive, could you live with that?
  • edited August 2010
    i agree with you, I'm just trying to narrow down the problem. It does need to be fixed, I'm just wondering if it could be something else other than a master cylinder?
  • edited August 2010
    If you have ABS, then it could be something there. Otherwise, if you aren't losing brake fluid, it almost has to be the master cylinder.
  • edited August 2010
    Sounds like the MC, had this problem on my 74 Nova only did it once and a while. What I found was if you would "very gently" push on the pedal it would go to the floor...try that...if you used normal pressure it was fine. What happens is if you gently push on the brake and it goes tom the floor, it means the brake fluid is getting past the seals. When braking normally the extra pressure expands the seals enough to provide normal braking.

    Replace the MC, and flush the old brake fluid and air out of the system.
  • edited August 2010
    When I had this problem, it was intermittent and ended up being the master cylinder, so knowing it is intermittent doesn't change my answer about the diagnosis. I don't know the answer to your other questions for sure, but I believe the answer is yes, a bad master cylinder MIGHT be causing your other symptoms. However, when you take the car in, don't tell them you have a bad master cylinder. Tell them your symptoms and let them check the whole brake system. After all, you might have more than one problem.
  • edited August 2010
    ABS cannot interefere with a braking system in such a manner as to allow the pedal travel to increase.

    This one sounds like a definte master cylinder to me.
  • edited August 2010
    The master cylinder is not causing the ebrake not to work. The ebrake is a completely separate system from the service brakes by design, so that if the service brakes fail completely they won't fail the emergency brake as well. I suspect your ebrake is out of adjustment. That's something that should be fixed when the car is in for the MC change (and I do agree with everyone above that you need to replace your master cylinder).

  • edited August 2010
    The master cylinder on my 71 Buick failed at the end of a 150 mile trip. Fortunately I was 2 blocks from home and nobody else was in the intersection. There was a little braking left, enough to get home and then had it towed to the shop. There was no warning and the brake light only came on as the pedal sank to the floor.

    This is not something you want to mess with, please get it fixed for your own sake.

    Ed B.
This discussion has been closed.