Strange Metallic Noise - 718 Cayman PDK

[PHB1969]

Car is a 2.0 PDK Cayman.
Not used much. Serviced at 2 years in September at 4229 miles.
Returning home today at c 4550 miles.
Was on the A1, car nicely warmed up. Took the slip road behind another car, not going fast 45-50 mph and off the gas, easing up on an uphill sliproad, not braking.
As the speed dropped, there was a noise that sounded very much like a load of metal bits being shaken in dustbin.....lasted 1-2 seconds, then a metallic rotational noise like something was binding/being dragged along.
I braked - all was ok - no problem
I set off from the roundabout slowly - no noise, no problem. I eased off, no noise, albeit wasn't uphill.
Was then in traffic so couldn't try anything again until next roundabout - all ok - tried in manual mode, all ok. eased off again, downhill, all ok.
Went uphill no noise.

Got home, checked under the car, the front and rear arches, nothing obvious. Took the cover off under the frunk, nothing obvious.

I do recall hearing a noise like the rotational / dragging noise when we came back from service, it was stopping at some lights - I thought it must have been a twig / small branch that dragged under the car (was surprised as I thought I would notice something that would make that noise).

Rang the OPC - they can check it tomorrow, but I'm not available. Booked in for 12th January for a check over......or bring it in if it gets worse.

Not worried as all under warranty but just wondered if anyone has any thoughts as to what it could be - instinctively I thought it came from the front, but might not be - them wondered if it was consuming its own gearbox.... Might go out in it tomorrow to see if it happens again....

 

[Terry]

Most likely caused by something getting caught in a brake disc, could be a small stone or twig.

it has happened to me several times and the easiest way to clear it is usually to reverse for a short distance and whatever it is will come out.

 

[AndrewT]

I agree with Terry’s suggestion, a small stone lodged between the brake disc and caliper or dust shield can make a horrible noise and may be more noticeable when cornering one way but not the other.

 

[PHB1969]

Thank you both - reassuring to know that this perhaps isn’t uncommon. It sounded extremely expensive!

just had a dental implant so not feeling too good - quite a lot of jaw pain so had some codeine....depending on the down from that might have a root around tomorrow to see if I can see anything.....

 

[Brian_Innes]

Did you by any chance drive over a recently patched road surface with gravel chips, as in the kind of pothole repair Council's sometimes do as a quick patch-up job? These patches are not easily seen, especially in the dark or in low light conditions. They often cover only a small localised area.

When your tyres are warm after a longish run, driving over stone chips or loose gravel will cause the gravel particles to adhere to the warm tyre treads and be thrown off against the inner wheel arches. That would match pretty well your description of the sound. Some loose gravel may also become lodged in the brake discs or brake callipers causing a rotating, binding sound for a short while.

Just my thoughts on a possible answer.

Brian

 

[PHB1969]

Taken out this morning, quite early. Went to a local Tesco car park which was empty as the store was closed and reversed a few 100 metres. Haven’t had any noise since the initial experience and none after.....

Did give the car a good clean.....very surprised at the amount of rock salt stuck in the barrels of the wheels....very possiblly something like that may have caused the noise.