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      06-11-2017, 12:18 PM   #1
320IN54
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Spongy Brakes After Pad Change

I just changed my brake pads yesterday and when I went for a test drive the brakes felt spongy and mushy. The car wasn't like this before the brake change and after some research it turns out that some air might have gotten into the system. How is that possible when I never opened the brake fluid reservoir or touched the brake bleeding system?
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      06-11-2017, 12:33 PM   #2
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Drive it around a few days, it will improve. Pads and rotors have to wear on each other a bit.
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      06-12-2017, 07:25 AM   #3
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Two ways air can get into the system without open the bleeders:

- Air can slip by the piston seal in the caliper. Usually you have a leaky piston seal when this happens, but it can happen.
- Brake fluid attracts and absorbs water from the atmosphere. Once water is in the brake fluid, the heat of braking can cause it to boil, and while not 'air', this will make the brakes feel spongy.

While you may want to wait a day, if you have not changed the brake fluid in the past 2 years as recommended, if the spongy feeling continues you should change fluid and bleed the system.
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      06-12-2017, 07:56 AM   #4
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Same thing in my Audi.

My theory: compressing the calipers/pistons for a prolonged time (during the brake job) allows any impurities (water or air) to accumulate into a larger, singular deposit.; which you notice the very first time that you apply the brake pedal, after the pads are changed.

I would've been suspect of the mechanic hitting me for a bogus repair (bleeding the brake lines), except for the fact that the work was done myself and a friend. So like you, I know that nothing was done to bugger the brake lines.


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I just changed my brake pads yesterday and when I went for a test drive the brakes felt spongy and mushy. The car wasn't like this before the brake change and after some research it turns out that some air might have gotten into the system. How is that possible when I never opened the brake fluid reservoir or touched the brake bleeding system?
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      06-12-2017, 08:06 AM   #5
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It's normal. The pads need to bed in and it'll feel firm again.
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      06-12-2017, 09:12 AM   #6
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Quote:
Originally Posted by racermp View Post
Drive it around a few days, it will improve. Pads and rotors have to wear on each other a bit.
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Originally Posted by Welcome to NBA Jam View Post
It's normal. The pads need to bed in and it'll feel firm again.
What they said.
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      05-25-2022, 04:13 AM   #7
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Hello All,
As this thread does not seem to have a solution I will share one of mine. I'ver registered to this forum to write it. I vent trough tens of threads regarding similar problems and most of them do not have any solutions or they had solutions I dried already.

I had exactly same "spongy" brake pedal feeling after rotor and pads replacenent.
I thought that it's because of new pads, that they have to set with new rotors but after few houndreds kilometers it did not change. In a matter of fact it got worse. So despite not openieng brake system during the change I've decided to flush brake fluid. I did it like 4-5 times, even in shop under pressure. It did help a litte bit but still not to the point I felt safe with pedal response. Next thing I did was to buy used master cylinder and replace mine with it, it did changfe feeling for a better but still not to the point it did satisfy me, so I thought maybe this new/used MC was damaged or I did damege it when I was bleeding my brake system (according to ATE you should not use pedal method because you can wear and tear cylinder seals, MC does not operate in max floor position normally as it does during 2-person bleeding method) so I bought new MC (OE ATE) and supprise, supprise it did not change a thing! Total waste of money. My last idea before I was going to swap my calipers/ DSC pump was to bleed out system once more, this time with all caliper pistons pushed in (to make sure that no air pocket reside in cylinder) during that I did not discover any air bubbles, but what I have discovered was that my rear left piston was stuck (I could not press it in with my fingers despite opened bleeding screw). I had to use tool to push piston back to the caliper, then press brake pedal to push it out. I did that couple of times to make sure that I will be able to push piston back with my hand. After that, I bled system once more with pressure bleeder and INPA, adapted DSC and it works perfectly. Brakes are sharp, pedal feels much better (1cm of pedal travel before it enagages in comparison to 50% travel before). If I would find it earlier it probably would cost me nothing to fix it, so it is worth a shot. Brake system is realy hard to diagnose...

I hope my explanation was clear enough, if you will have any questions, just let me know
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      05-25-2022, 06:27 AM   #8
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You need to bed the new pads in correctly. There are lots of video's by various pad manufactures on how to do this procedure. There is nothing wrong with your car or the calipers.
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