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Old 07-13-2014, 03:20 PM   #1
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disc brake dilema


Help, I just installed new pads on my 97 pont. trans sport pumped up the brakes with the engine off, started engine and the pedal goes to the floor, wont pump up. What did I do wrong

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Old 07-13-2014, 05:54 PM   #2
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disc brake dilema


Is the brake light on the dash on?
That would mean half the brake system is not coming up to pressure, usually due to either a leak or air in the system.

Did you open the hydraulic system in any way, such as loosening the bleeder screws or removing the brake hose from the caliper? If so you may have allowed air into the system and the brakes will need to be bled.

Check the brake fluid level in the master cylinder, is it low? Are you losing fluid onto the ground? You may have blown a brake line after disturbing it. Lines can get rusty and moving things around can disturb the bad spot enough to cause a break. Twisting or pulling on an already weak brake hose may cause it to begin leaking.

If you pushed the pedal hard down to the floor while pumping the brakes up you could have damaged either the brake booster or the master cylinder, this isn't common but possible with some vehicles.

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Old 07-13-2014, 06:02 PM   #3
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disc brake dilema


Did you bleed the brakes?
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Old 07-13-2014, 06:42 PM   #4
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disc brake dilema


Thanks guys, yes I just bled all 4 corners with the same end result. I do hear a wooshing sound from behind the brake pedal when I press down, reminds me of when the booster was bad in my bronco.
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Old 07-14-2014, 06:41 AM   #5
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disc brake dilema


Did you keep the reservoir topped off or did you let it get air into the system?
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Old 07-14-2014, 08:00 AM   #6
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disc brake dilema


The whooshing noise you hear is normal, that is the airflow through the booster inlet. Did you open the system up at all?
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Old 07-14-2014, 10:09 AM   #7
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disc brake dilema


Hey thanks you guys, No I did not open the system, I was talking to a mech. friend of mine and he thinks I might have blown the seals in the master cylinder when I pumped the brakes up. any thoughts on this. PS I did have the resivoir cap off during the pad replacement.
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Old 07-14-2014, 01:36 PM   #8
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disc brake dilema


No idea. Done many pad replacements but never had that issue. I can't see how pumping them up with the car off is going to do anything unless you pushed down hard enough to break the pedal. Did you find any fluid anywhere? Was the cap on tight? You said you bled the brakes, all the bleeders tight and no fluid coming from them? You bled the right rear, then left rear, then right front, then left front, in that order, correct?
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Old 07-14-2014, 03:39 PM   #9
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disc brake dilema


I've done a lot of pad replacements and not once was it necessary to bleed the brakes afterward.
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Old 07-15-2014, 12:13 AM   #10
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disc brake dilema


Whooshing noise during braking and pedal going down is leaking brake booster diaphragm. You busted it doing pumping without engine turned on. No, it's not "normal" noise.
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Old 07-15-2014, 08:07 AM   #11
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disc brake dilema


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Originally Posted by ukrkoz View Post
Whooshing noise during braking and pedal going down is leaking brake booster diaphragm. You busted it doing pumping without engine turned on. No, it's not "normal" noise.
Not how this failure mode would manifest. It should evacuate all of the vacuum after 2-3 applies with the engine off, then go solid. This could not cause the diaphragm to damage.

If the booster has a leaking diaphragm, you would have an overly solid brake pedal with no vacuum assist. If you have a spongy brake pedal, it means you have air in the system or a leaking master cylinder. It would be very coincidental if there were no soft pedal symptoms before the pad change and the master cylinder failed during the pad change.

I have my money on air in the system, or perhaps a bad master cylinder. If the MC is indeed the culprit, make sure you bench bleed it before installing on the vehicle.

I have 8 years of experience in brake system testing/engineering
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Old 07-15-2014, 09:10 AM   #12
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disc brake dilema


X2. The 2 man way to bleed brakes involves someone pumping up the pedal with the car off. It didn't damage anything. I'm going with air in the system.
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Old 07-15-2014, 09:42 PM   #13
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disc brake dilema


If your brake booster fails, you often have a very hard brake pedal. You might still be able to stop the vehicle, but it will require a great deal of effort to do so. The first thing to check is the vacuum line going to the booster. Next, inspect the check valve that might be located in the vacuum line somewhere. Sometimes they're part of the feed line and cannot be accessed externally. If this type of check valve goes bad, you replace the entire vacuum hose. This check valve allows vacuum to go to the booster, but not back to the engine. When brake boosters fail, it's often a result of a master cylinder failure. Sometimes when a master cylinder fails, it leaks fluid into the brake booster. This can sometimes eat through the rubber diaphragm in the booster and cause it to fail. Other times, I've seen the return spring in the booster break and rip the diaphragm. Sometimes you can hear a hissing noise under the dash when a brake booster fails. This is the vacuum escaping. This vacuum loss can also cause engine performance issues. Either way, the fix is the same: Replace the brake booster.

http://www.ericthecarguy.com/faq/sol...oosterProblems
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Old 07-16-2014, 06:57 AM   #14
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disc brake dilema


The first thing to check is the vacuum line going to the booster. Next, inspect the check valve that might be located in the vacuum line somewhere. Sometimes they're part of the feed line and cannot be accessed externally. If this type of check valve goes bad, you replace the entire vacuum hose. This check valve allows vacuum to go to the booster, but not back to the engine. When brake boosters fail, it's often a result of a master cylinder failure. Sometimes when a master cylinder fails, it leaks fluid into the brake booster. This can sometimes eat through the rubber diaphragm in the booster and cause it to fail. Other times, I've seen the return spring in the booster break and rip the diaphragm. Sometimes you can hear a hissing noise under the dash when a brake booster fails. This is the vacuum escaping. This vacuum loss can also cause engine performance issues. Either way, the fix is the same: Replace the brake booster.

http://www.ericthecarguy.com/faq/sol...oosterProblems


Quote:
Originally Posted by ukrkoz View Post
If your brake booster fails, you often have a very hard brake pedal. You might still be able to stop the vehicle, but it will require a great deal of effort to do so.
Yes but the OP states that the pedal goes to the floor.

Quote:
Originally Posted by ukrkoz View Post
Sometimes you can hear a hissing noise under the dash when a brake booster fails. This is the vacuum escaping. This vacuum loss can also cause engine performance issues.
This is true during steady state. If the pedal is not applied and there is a hissing noise, then the booster indeed has a vacuum leak, the pedal will likely be hard, and the booster has failed.

The noise of air whooshing while applying the pedal is the sound of atmospheric pressure replacing the vacuum in the booster. Perfectly normal. Some vehicles louder than others.
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Old 07-22-2014, 10:55 AM   #15
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disc brake dilema


Disk brake contain hydraulic pressure system as well many kind of disk plate are available while pumping the brakes up you could have damaged either the brake booster or the master cylinder and chek the fluid also.

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