erik_plus8

Car is a 981 CGTS 2016 M/T with now just under 7000km on the clock. Owned it from new (January -16). Until now, no issues whatsoever.

Problem: At very low speeds, pedestrian even, there is a very faint sound just as I start to apply the brake. It is very similar to the sound the rear parking sensors make as you go into R, to make you aware they're there and working (I guess). But this sound is much weaker, and shorter. There is no warning anywhere on the dash or any stored messages/errors.

I can replicate it whenever I want, but only at very low speeds, probably because it's not detectable as soon as some road noise comes in.

I first thought brake fluid level could be low and the warning just triggered because level sensor dropped when fluid goes out into the system. But the level is fine and also, the sound doesn't come if I reverse and apply brake, just when going forward...

The car feels its normal, wonderful self in all other driving conditions. I could maybe ignore this but A: something has changed and B: I have a track day coming up in two weeks and I do not want to have a bigger issue just before or even at the track...

I do not think it's a chip or stone between the disc and brake shroud because the sound is only there when pressing the brake. Also, the character of the sound is more a "note" (like a warning signal, "ding!") than a "squeak". If you see what I mean.

Any ideas? Thanks!

Pep!RRRR

Try doing some hard braking at higher speeds to be sure everything is bedded nicely. Maybe the sound will go away. If you are doing a track day will you also be flushing the brake fluid? Bleeding the brakes is never a bad idea.

I assume your pads are relatively new?

erik_plus8

Thanks! Pads are as old as the car, so too the brake fluid. Will have it changed in a month. Will try to do some high speed braking tmw. Strange thing is this sound occured yesterday, have definitely not had it before. And everything should be run in and bedded at this point in time, I would think.

terbiumactivated

Did you visually inspect the rotor faces for any scoring? Personally, I doubt it's the fluid. I change mine on the intervals to keep Porsche service interval perfection. Yet in the scenario you present it's hard to believe the fluid is making this noise phenomenon.

erik_plus8

Yep, rotors checked - no damages. Since the sound comes as soon as I start some travel on the pedal, but before there's any retardation (i.e. the pads hit the rotors) I don't think there is something at the wheels.

I went into my P-dealer yesterday and had the very helpful service manager plus a technician to take it for a spin. They hear the sound, they got it on film, will send it to the swedish importer to create a warranty issue. They think it's the booster making the noise. On my question why it doesn't come when standing still or reversing, they say the booster work differently in different driving modes. Haven't heard that before, but what do I know

So, we have booked a slot for changing booster, end of September. However, the importer has to approve the warranty issue and that is a process we will see the outcome of in a couple of weeks.

terbiumactivated

Awesome sounds like you are on the way to resolution. I've never heard the brake boosters were variable either that's interesting to say the least.

JCtx

I'm pretty sure the dealer was talking about the ABS module, and not the vacuum servo assist. Both can be called 'boosters'. I've never heard of any vacuum servo being variable, and you'd certainly feel the difference... IMMEDIATELY. Plus there're no wires whatsoever on either the servo or on the vacuum hose, so can't be variable. Like I explained on the other forum (don't understand why people post simultaneously on 2 forums, but whatever), the ABS module retracts the pads closer to the rotors (actually touching them) on sport+ (and maybe sport; not sure), to minimize reaction time. And when it rains, it actually applies pressure to the pads to heat up the rotors/pads and dry them. So if it's the ABS module, maybe it's malfunctioning, thinking it's raining. Who knows. But unless there's a vacuum leak, it'd be the ABS module. And before authorizing anything, I'd make damn sure that's the issue, and not just a little bit of pad deposits, which would be perfectly normal. Good luck.