phow

I hope this post can be helpful to someone that may be going through the same frustration I have been for the past 2 weeks. I realize I could have just taken the car to the dealer (and was about to) but I prefer to fix small issues on my own if possible.

There was a very noticeable rattle/creaking coming from the driver's side dash behind the gauge cluster and just in front of the windshield near the A pillar. The noise only happened when the vehicle was in motion and was most noticeable over rough surfaces. The best way I can describe the noise is that it sounded as if the windshield was loose and rattling/creaking slightly.

I immediately assumed the noise was coming from inside the cabin and begin checking all panels around the dash. After several hours of pushing and pulling on every removable/moveable part in the vehicle, I came to the conclusion that the noise was being generated in the frunk area of the vehicle and traveled into the cabin.

Lesson #1: Cabin acoustics really are a bitch, so don't assume where you hear the noise is the same place it is originating from...

After poring over the various threads in on the boards, I concluded one of the following must be the issue:

1. Gas/Fuel Tank Mounting Pads - Apparently these move out of place and cause a noise similar to what I was experiencing that sounds as if it is coming from behind the driver's side dash.

2. Plastic Cover in Frunk - The plastic cover has reported to vibrate and cause a similar noise as described.

3. Suspension Mounts - These dry out and/or become worn and will cause a similar noise as described.

Troubleshooting Steps:

The first thing I recommend doing is removing the plastic cover in the frunk and driving the vehicle without it. If the noise goes away, the cover is most likely the culprit and some felt tape in the right places will solve the issue. Unfortunately, this was not the cause of my issue.

The second step I took was to monitor the noise with various levels of fuel in the gas tank. The noise was not different from near empty to full. It is reported that the gas tank pad issue will be louder on a full tank. While this isn't a foolproof method of diagnosing this specific issue, it was enough for me to move onto the suspension mounts.

I decided to check the suspension mount on the driver's side but lifting the vehicle off the ground and allowing the driver's side wheel to extended fulling for one hour. I then lowered the vehicle and immediately began driving it before the suspension had a chance to settle. The noise was gone...

^ The noise remain absent for the next 24 hours. The following day, it came back. Very faint at first and progressively got back to full volume. This definitely lead me to believe the noise was suspension related.

I took some rubber silicon lubricant and sprayed the top suspension mount. I allowed this to soak for several hours and drove the car again. The noise is gone.

^ This seems to have solved the issue as it has not returned for several days. I do plan to make an appointment with the dealer and have them check the mounts and see if they should be replaced.

I hope this helps anyone else with the same or similar issue get to the bottom of the cause. Noises like this can really take away from the enjoyment of such an amazing vehicle and I'm glad this one is behind me. At least for now

Porsche_nuts

Excellent.

Thanks for the writeup!

dflowerz

Thanks for the info. How many years/miles on your car? Garaged or kept outside?

phow

No problem! 2015 991 C2S w/ ~10k miles. Garaged.

DerekS

Did the suspension mount make any noise when you jiggled it?

I already investigated that mount, and it was very secure. I have not tried lubricant yet though.

WD40 ok, you think?

I would pay $1000 cash to be rid of this noise. Hell I'd pay $2000. It significantly detracts from my enjoyment of the car.

phow

Good questions!

No, the mount made zero noise and was completely secure when I first inspected it. Even pushing down on the vehicle and compressing the suspension slightly made no odd noises.

Do not use WD40. You want to use a silicon based lubricant for rubber. WD40 will just kill any lubrication you have left and dry out the mounts further.

I felt the same way you did. I was to the point that if the dealer couldn't figure it out, there was a speciality shop I was willing to pay whatever it took to get rid of the noise.

My suggestion would be to run out to the local hardware store, pick up some silicon spray and soak the mount. After 30-60 min you should notice an immediate decrease or elimination in noise if a dry mount is the cause.

DerekS

Ok I got some pure silicon lubricant and practically filled the mount with it.

Giving it 20-30 to penetrate and will report back.

If this fixes my long standing annoyance, you're my hero!

DerekS

My sound, for reference: http://tinyurl.com/targarattle

It doesn't have the "beer cooler" squeak of the tank pads.

phow

I hope it works out for you! Your noise does sound similar but it is tough to tell for sure from the video clip.

Driven991

Great Post Man! Thanks. I have an annoying rattle in the rear cabin area of my 17 C2S that I have got to start figuring out. 3500 miles on car and it is very annoying.

DerekS

Well, it wasn't the mount, and I've already eliminated the other two causes.

I was driving home feeling despondent. I've had this problem for almost two years now. Maybe I should just sell it and move on with life?

Then I remembered you pointing out that the source of the noise can be deceiving.

I had a passenger put her head near the noise - which I swore was coming from the instrument cluster - and she said it was definitively coming from the top of the windshield.

My last service adventure around this problem said the same thing, and replaced something in the trim there, but the problem remained.

Armed with the certain knowledge that it's coming from the top of the windshield area, I started probing. Does pressing on the trim change it? No. Pull over and thump on the top. Anything loose there? No.

Then I remembered the pop up windstop on the Targa. It has two positions -low and high- and I always stow it in low. Furthermore, it has always been sticky and difficult to toggle positions.

I decided to try raising the windstop and closing the top in the upper position and...the problem is gone!!!

What I think is happening - the windstop is stuck down and has just enough clearance to rattle against the top in an irritating way. When it's in the upper position, there's enough spring force to keep it snug against the top and silent.

My next course of action will be to resolve the sticking and see if the problem goes away in both positions. But for now I am so happy to finally be rid of this noise!

It's sucks to drive a 140k car that rattles like a 25 year old Honda!

phow

Congrats!

After only 2 weeks of dealing with mine, it felt really great when it was finally gone. I couldn't imagine dealing with it for 2+ years... Must have felt liberating to finally have it resolved.

I feel like there is a balance with noises in this particular car. I would never call this car quiet, and it often creaks/groans a bit under certain conditions. However, I'm overall very accepting of that and even chalk it up to being part of the 911's charm. There is definitely a difference between normal lightweight sports car noises and something that just sounds mechanically wrong.

You definitely can't be OCD about odd sounds and own a 911... But that also doesn't mean you need to ignore something that clearly sounds wrong with the car. Especially with a price tag north of 100k...

DerekS

Well, my 997 was definitely not as noisy as this one.

I often think I made a major step up in cost and a major step back in satisfaction.

A huge part of that is the squeaks and rattles of which I've had a ton.

Scottish Pete

I had a really noticeable clunk in the right side when driving around a corner hard. Worried about whether it was PASM or PDCC or some other sophisticated suspension problem. I put my hand down flat on the floor behind the passenger seat to see if I could feel the clunk when it happened as I cornered (isn't one handed power steering in newer 911s handy).
A metal water bottle rolled across my hand that my sister had left behind her passenger seat. Sister had returned home months earlier.
Get a flashlight out and check under the seats first when troubleshooting odd noises.

mtony

I think I was one of the first people to have had this problem. The dealer ordered a new mount, but after almost two years after spraying rubber conditioner on it, I'm happy to report that the rattle never came back!