1990nein

So I park the car, shut the engine off., and there is a whining sound coming from he front end of the car. Sounds almost like an electronic hum but also similar to when you creep very slowly and the brakes squeak. Got out, took a look around the car, and it sounded like it was coming from the front brake area. Then I gave the brake pedal a good kick, and it stopped whining

Is this air in the brake lines? It sounds like creaky brakes creeping really, really, slowly.

Edgy01

Air doesn't just magically get into a brake line--unless you did something to cause that. Has anything been serviced lately?

There's a lot going on within the front area of a 997, so unless you can isolate the area a little tighter than the "...front of the car..." we're just going to be guessing.

1990nein

I think I've narrowed it down to the brake area. Regarding air magically appearing in brake lines, it actually does, especially if your car sees the track often.

Recent work is tires and alignment. I haven't ruled out the possibility of it being there but since the sound stops when I hit the brake, my guess its something with the brake system.

This particular GTS has 28,000 miles with no brake service yet. Hasn't seen any track/heavy use. The sound has occurred twice, both times after 1 semi hard braking on cool brakes.

Any guesses?

Derek@TRG

When you bring your brake fluid to its boiling point it will produce gas or air in the lines, if this happens you will have a soft pedal with long travel, you didnt mention this so it sounds like that is not the problem. Next time you hear the noise pop your front lid and listen around the brake fluid resivoir area, your ABS pump is just below and could be the source of this noise. I cant think of a reason why it would run though.

Does this happen on every shut down? intermitent?

Macster

It is hard to imagine how brake lines could generate noise after the engine is shut off.

The only thing I have heard from that area of the car after engine shut off is sometimes the sound of a radiator fan spinning down. The noise is short-lived though lasting just moments and certainly not long enough to get out of the car and walk around that area and come back and depress the brake pedal, at least at something under the speed of Flash.

It could be you were hearing some noise from the A/C system, caused by some residual pressure bleeding from the high pressure side to the low pressure side.

Yet another source of the noise would be something in the vapor recovery system of the fuel tank.

It is even possible that there is some air in the cooling system, a pocket of air perhaps in a radiator, and the heat load from the engine raised the cooling system pressure some to force coolant through/past this air.

All WAGs of course.

You need to demo the noise to a professional Porsche tech and get his diagnosis.

Sincerely,

Macster.

1990nein

The pedal still feels good, I doubt it'll need a flush for some time. I should clarify that although it sounded almost like an 'electronic hum', I am almost certain it is a mechanical sound. It just didn't sound like a motor whirring.

I haven't been able to replicate the problem, but I'll be sure to record the sound next time it happens. There is another odd behavior with the brakes that might be related.

It happens at low speeds, particularly when the wheel is turned and the brake pedal is depressed quickly (i.e. during a 2 point turn to back into a parking slot). There is a grinding noise/shudder as I get close to full steering lock and full engagement of brakes. If I remember correctly it would also make the steering wheel jerk and shudder.

I've hit the ABS before and the grinding feels and sounds very similar to the noise, but it seems unusual for it to be happening at 0-3mph. Anyone else notice this?

user 72902

You'll know for sure when you have air in your brake lines.

997_rich

when you shut the car off, the sound you hear in the dash is normal. not sure what it is but to me it sounds like a hard drive being written to or something.

the grinding while braking and turning isn't normal. I'd have that looked at. Do you have a 4S?