Apologies if this has been covered before, but I'm experiencing an occasional loud clunk from the back of my 991 GTS when I come down off a speed bump. My first thought was that it was the rear of the car bottoming out, but the sound sounds like it's coming from the top of the engine (almost like there's something banging around in the trunk of the car, if it had a trunk in the back, or on the back seat). If I go over the bumps slowly it doesn't happen, so it could be a case of 'doctor doctor it hurts when I do this / well, don't do that', but maybe my occasional desire to get across town at a reasonable speed has revealed something in the car that needs looking at.

Has anyone experienced this before? Does the sound of the back of a 911 touching down sound very different from the front lip scraping a bump, because of the extra weight? Should I just slow down over the bumps because I'm not driving a Boxster anymore?

Any info appreciated - thanks!

 

you *could* be bottoming out the exhaust and/or engine block and the noise appears to be coming
from the top of the engine compartment...

If you can get under the car and look for any scuffs etc on the lowest parts of the engine and exhaust system

p.s
you are more likely to "ground" metal at the rear than "plastic" at the front ... hence if you are bottoming it sounds
metallic and from the engine compartment...

 

Maybe the blue shipping blocks aren't removed.

 

My Costco has ridiculously tall speed bumps and I actually experience the clunk as well when I go over them at more than 2-3 mph. There's no damage or scraping under the rear so I'm pretty confident that the suspension was just bottoming out.

 

I also had a clunk coming from the rear. Drove me nuts until I figured out that the rear set was not latched. Then I heard another clunk and found out that the rear trim inside the car under the rear window was not properly seated. The tint guy had removed it when he did the windows. Everything is quiet since.

Point being these things are sometimes hard to track down - don't overlook the simple stuff.

DaveGee

 

In my situation it was loose sway bar linkage.

 

That's a likely culprit

 

I had something similar...it turned out that I had a plastic water bottle half full under the seat that was making the noise

 

Thanks all. I called the dealer and they said to bring it in for a look. Will let you know.

 

I'm betting its the anti-roll bars ...

 

I've had a very similar issue recently. Just started happening about three weeks ago. Fairly loud, obvious, metallic-sounding clunk coming from right rear over certain low-speed bumps. It's not rough roads that cause the noise, but instead large bumps like speed bumps or entering sloped driveways at an angle. It seems to be chassis flex that creates the conditions for the noise.

My dealership had the car for a week trying to locate the source of the noise, with no luck. Had it up on the lift, checking tightness of all suspension components, including various linkages and upper suspension mounts. They drove it multiple times with the "chassis ears" installed, but couldn't pinpoint the noise. The chassis ears are multiple microphones that get installed around the bottom of the car. A tech then rides shotgun with a set of headphones and a multichannel receiver to find where the noise is located. No dice.

The noise has lessened on its own over the last couple of weeks, but it's not very satisfying to not know exactly what causes it.

Keep us updated.

 

Yup, that's what I had.

 

BMW dealer used those things to identify a maddening squeak on my M3. Worked wonders, found something they never would have been able to pinpoint without using the ears.

 

It's in the shop today and they've just called to say it was a stone caught in in the sway bar. Apparently they've seen this on 991s a few times.

I had a slightly mad morning getting there at 7am to make sure I could find a bit of road bumpy enough to make the car make the noise when I took the tech guy out in it. Nothing worse than the old 'but it always does it at home'!

 

I have the same noise but i couldn’t find the cause until now. Did you solve it? What was the cause? Thx