Cay981

When driving over cobblestones, there is a disturbing rattling noise coming from the dashboard, I assume.
Does anyone here have or had this problem and if so would like some tips and advice, thank you.

nhnguy12

I've had two separate AC vents cause rattles. Diagnose by pressing down on each vent while driving over uneven roads. Downward pressure on the offending vent made the noise go away. I then pulled the vent out of the dash (5 minute job with the proper trim tool) and liberally applied silicon grease on the metal tabs that had loosened with age.

Cay981

It doesn't come from the air vents but rather in or behind the dashboard, almost like a knocking sound.

CaymanCarver

Rattle noises in the Cayman can be deceiving.
Try reseating the seat belt on the passenger side, it can make a rattling sound that appears to come from someplace in the dash.
Or Take a friend for a roll and see if it persists.

Robertf1997

I have a 2013 boxster S. Car rattles and knocks from dashboard really bad all the time and drives me crazy. According to my service records, previous owner had Porsche dealer in Oregon remove dash to attempt to sort. Guess even with removing dash and looking they couldn’t find what it was.

TMc993

Sources of "dash noises" I've experienced in my 2014 Cayman:

• The pads that isolate/insulate the fuel tank that can eventually compress, causing a bumping/knocking sound under certain conditions. It seems to be a fairly common condition and is remedied by replacing said "pads."
• Less common is the loosening/failure of the upper strut tower bearings, causing a bumping/knocking noise under certain conditions. If found loose, torque to spec and see if that remedies the issue (Mine were replaced under CPO warranty).

I also know of another Cayman that had a loose steering column (No idea why it was loose) that rattled.

All of these things caused noises that were transmitted through the unibody and sounded like they were coming from behind/under the dash.

TEF

It's hardly mentioned on the 981 forum, but the 987's, has ball joints on the front lower control arms (called the coffin arms by the Brits due to their shape) that ware and cause a knocking sound. On my 987 BS, the noise would appear at slow speeds over bumps or rough pavement. Please note that the 981 has a similar front end design. To fix this, one has to replace the LCA's because the arm and ball joint are one assembly. On the 987, repair not fun, but still a DIY job that did not affect the vehicle's alignment. And one more thing, jacking up the front will not reveal the problem as the front is under tension from the springs and shock assembly. From what I can tell, the problem occurs not so much from ware, but from a damaged ball joint boot or water getting in and damaging the ball an socket.