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Brakes soft then not - no brake work done

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Old 05-18-2018, 09:17 AM
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personalt
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Default Brakes soft then not - no brake work done

Yesterday my wife complained that brakes in her Cayenne were soft. I drove it last night and felt it the same. Peddle would sink but what was interesting was if you let it come back up a hair and pushed it down a second time it felt a lot stronger. Fluid level was topped off so doesn't appear to be any leaks or air introduced in to system.

Car is under warranty so figured we planned to take it in but today it is not happening. Is there any brake issue that would cause the brakes to be sometime spongy but not others?
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Old 05-18-2018, 10:54 AM
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Eskimo1
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Doubt this is the reason for your case, but when wheel bearings start to get slop in them, this happens. The brake rotor moves around and pushes the pads back into the caliper, and when you first press the pedal, it has to take up that gap. A little bit of that is normal, as manufacturers try to pull the pads back a bit for better fuel economy.

More likely would be dirty caliper pistons,, catching on the piston seal when you press the brakes, but that friction pulls the piston back further than normal.
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Old 05-18-2018, 12:31 PM
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What year and how many miles. Maybe flush the brake fluid and bleed. The couple times I have done that the peddle firms up.

I still a bit soft though.
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Old 05-18-2018, 02:42 PM
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Brake fluid needs to be flushed and replaced every 2 years as Porsche brake fluid is very hygroscopic. It absorbs moisture. Old fluid makes the brake pedal feels soft. Happened to my 2013 CTT.
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Old 05-18-2018, 06:15 PM
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personalt
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Originally Posted by Eskimo1 View Post
Doubt this is the reason for your case, but when wheel bearings start to get slop in them, this happens. The brake rotor moves around and pushes the pads back into the caliper, and when you first press the pedal, it has to take up that gap. A little bit of that is normal, as manufacturers try to pull the pads back a bit for better fuel economy.

More likely would be dirty caliper pistons,, catching on the piston seal when you press the brakes, but that friction pulls the piston back further than normal.
Yeah I saw some videos sighting this bearing as a possible problem, but I don't think it was applicable to me as when it was happening the paddle was dropping even if I was sitting in the driveway. You might be onto something with the caliper piston getting hung up. Especially with it coming on all the sudden and then not happening the next day.
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Old 05-18-2018, 06:21 PM
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2012 with 60k. I have the car for about a year-and-a-half but not sure if they did it for I bought it as cpo. I was thinking about doing the flush. Only concern I had was if I did the flush and it didn't fix the problem and then I brought it in they might think that I did some brake work and introduced to Erin to the system. I have about four months left on the CPO warranty, which I think covers brake systems. I would think the CPO warranty would cover any issue other than the pads and maybe the idea that it should be flushed, but I could be mistaken

Originally Posted by Newegg View Post
What year and how many miles. Maybe flush the brake fluid and bleed. The couple times I have done that the peddle firms up.

I still a bit soft though.
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Old 05-18-2018, 07:22 PM
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Originally Posted by personalt View Post
... I bought it as cpo. '''
No brainer solution. Take it in to the dealer. Let them solve the problem(s). You might be out of pocket for a brake fluid flush.
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Old 05-22-2018, 01:43 AM
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And that's not really out of pocket as the dealer should be the one doing your fluid to get 100% of the fluid out of the system.
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