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I have already bled brakes and changed the master cylinder. What would be the next step to try to fix the brakes. The brakes still go to the floor.

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    What year/make/model of vehicle is this? How did you go about bleeding the brakes (step-by-step)? Did you bench bleed the master? – Pᴀᴜʟsᴛᴇʀ2 Nov 28 '15 at 14:19
  • If you pump the master cylinder does the fluid level drop? – mikes Nov 28 '15 at 22:52
  • When you say it goes to the floor, does it do that without pressing the brake pedal, or only when you press it? – HandyHowie Nov 29 '15 at 18:59
  • Are you losing fluid? What was the original symptom that caused you to need to change the master and bleed the system? – JasonJ Nov 30 '15 at 13:38
  • Does the vehicle have ABS? If so, did you bleed the ABS pump? – rpmerf Nov 30 '15 at 17:36
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Turn the car on and press the brake to the floor. When you release the brake-- listen for a kind of hollow wind sucking in from under the dash. If you hear a hollow sucking noise it means your Power Brake Booster is failed and you need to replace your Power Brake Booster. The noise can be faint or close to none at all but if your pedal is still going to floor after changing the Master Cylinder then it is likely that the Power Booster is gone.

  • I don't think that would cause the brakes to "go to the floor." The brake booster simply assists in pressing the pedal by using a vacuum line to increase the driver's effective force against the pedal. If the booster broke, it would increase the effort required to brake, but not cause a loss of pedal response. Then again, I could be wrong. Less experience here. – Hari Ganti Dec 2 '15 at 10:21
  • A vacuum leak in one of the hoses can cause the brake booster to not function properly. Inspect all vacuum lines for leaks and replace them if they are defective. My old Mercury Mystique had an issue with the vacuum line. It was constantly rubbing against the firewall and wore a hole right through it. – Jason Hutchinson Dec 2 '15 at 17:26

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