Rear hatch rattle at hwy speed

Hear is a stumper maybe some have experienced. I have an unusual rattle that is metallic sounding, constant at hwy speed and intermittent at surface street speed. It doesn't seem to be affected by hard bumps, but rather by high freq vibration. It's louder with the carpet cover over the engine cover removed, but I don't think it's coming from the engine compartment as I pulled the covers and checked connections and air box with the motor running. It's coming from the driver's side rear hatch, maybe near the shock tower or stowage compartment. Obviously I checked the compartment and have even pulled the side panel and added felt tape liberally. Oh, and when I bought the car in July it wasn't there, but is always there now when the above conditions are met. The sound is very similar to when an old car got bad gas and knocked and pinged, but this sound isn't related to engine RPM as its there evenly at WOT and idle. I have an appointment Wednesday to get it checked. Any ideas? I plan to report back with results from the dealer.

I recently had a rattle coming from somewhere back there. I eventually found it. It was the weight for the rear trunk and also the 3rd brake light that was vibrating against the glass. I fixed both issues and no annoying vibrations anymore.

Hello evannever, I had an issue that was similar in description. What I found was that the top winding of my passenger's side rear spring was making very light contact with one of the heads of the three rear strut mounting studs. It is designed for the spring to not make contact by means of the installed top of spring insulator however mine shifted. If you put a couple spring compressors on the spring to reduce the pressure, you may be able to reposition the spring's insulator. Regards, Joe P.S. Also, the noise lessened or abated in the rain due to the water lubricating the metal-to-metal contact.

Joe, this sounds like a possibility! Was there any way to diagnose this without compressing the spring? I take it you lifted the car, pulled the wheel and then compressed the spring. Any other disassembly or where you able to just reposition the insulator? We don't get too much rain here in S Texas, so I haven't checked in the wet. Acosta, I should have mentioned; I've done just about all the interior fixes you could do including the trunk clunk and foam tape around the third brake light. However, thanks for the input.

Joe, I took a quick look this morning with a flashlight at the top of the spring perch and nothing appeared out of place, but I will put it on the jack tonight and really look. Like you said, the inboard stud isn't visible. The sound you're describing could be dead on. It really is a metal on metal sound but from inside the car its slightly muffled. Thanks again. If I see anything I'll get some pics and post 'em.

Oh snap! I think thats whats rattling in mine too!

Hello evannever, Mine didn't look terribly "out of place". All you need is for the steel of the spring winding to simply contact the head of the stud and you may get the noise. Best regards, Joe

Joe, apply a little petrolium jelly to the sides of the rear hatch rubber guards next to the shock towers. Go for a ride. if the noise is gone you know the problem.

Hello blue-eyes, I appreciate your suggestion however I eliminated my noise two years ago by preventing the top winding of my rear spring from contacting the strut mounting stud. My posts are an effort to help evannever eliminate his problem which describes very much like the one I had. Thanks, Joe

Well guys, I did some more testing including having a buddy drive while I poked around the back. I've changed directions for looking into a fix. Here's what I found: The sound is actually coming from the vicinity of the stowage compartment behind the driver. Now, there was nothing in the compartment and the panel itself is solidly mounted. I also noticed that the sound, while present at WOT and cruising throttle positions almost completely goes away at Idle when at hwy speed. Because of all this, I think it's something connected with the air induction. Possibly a piece of debris in there or a loose connection. I had already check the mounting of the airbox cover and filter, but I'm going to pull the side vent, filter and restricter plate cover and get a good look through there. I know I should probably let the dealer handle this, but something about considering myself a pretty handy wrench and a man who takes care of his business compels me to keep poking around. Thanks for all the tips and suggestions. Whatever I find, and I or the dealer will resolve this, I will post up for future reference.

Update: It's fixed but I don't know how for sure. I took it do the dealer to have some other work done and they took it for a drive. Long story short: They said they couldn't guarantee a warranty fix because I had pulled panels chasing down other rattles. The service manager offered to let the tech ride with me to help pinpoint the rattle so I could fix it on my own ( I thought that was a nice compromise ). The tech was fairly certain it was coming from inside the cabin in the vicinity of the drivers side storage compartment or rear shock tower. I took the car home and tore into the interior. When I removed the cover over the shock tower, I found nothing. So I employed Joe's advice (above) and checked the spring perch. This was a scary job alone at 9pm on a work night, but I managed to un-seat then re-seat the bumper at the top of the spring with a couple borrowed compressors from Autozone and some frustrated pushing on the spring (the re-seat). Still the rattle was present. Then I went after the storage compartment behind the drivers head. With the shock tower removed I was able to reach under the compartment and root around with my hand. There is a big piece of baffling in there and a rubber boot that separates the interior from the intake plenum. Nothing felt loose but I removed the baffling and drove the car (with the compartment still in) . The rattle seemed unchanged and I felt like I was done for the night (about 11pm). Defeated, I parked the car, shoved the wad of baffling back in as best I could and went to bed trying to think of other solutions (like dynamat). The crazy thing is I haven't heard the rattle since. I think it was either the wiring bundle or something with the plenum/rubber boot under that compartment. Shoving the baffling in there so there was tension, rather than the way Porsche placed it in there must have applied pressure to whatever was causing the rattle. :crazy:

See my post for a simple, cheap fix.