Just got a 2008 350z with 25k miles. Car literally has the new car smell. Aside from rear differential bushing that needs replacing due to age, everything else is pristine.

EXCEPT THAT DAMN RATTLE coming from badk or the car. Only happens when there is a bbump or uneven road, but it seems to be getting worse.

It sounds like it's coming from trunk, not under the car, and it feels more like passenger side area of the trunk. It mighIt be the trunk sway bar, or the trunk latch. I've spent so much time back there looking for the cause and nothing seems out of place. There is a plastic panel right behind passenger seat that wasn't stuck to the frame like other side, but I don't think that's enough to account for such loud rattle.

What should I check for ? Searching the forums didn't help

It's literally only thing wrong with the car

 

Mine had that , but it was a rear suspension bolt burried under the carpet. Brand new bolt , was somehow put in my interior probably at the factory

 

Can you be more specific? I lifted the carpet and chekced all the tools on passngee side in back of trunk are secured. Where was that bolt exactly?

 

Congratulations on your 350Z! To solve this rattle, start by checking that the spare tire, the jack and the tools in the trunk are well fixed. Also inspect the trunk lock and the jacks to make sure they fit properly. The loose plastic panel behind the passenger seat could be a cause, add padding if necessary. Also look at the rear belt fasteners and any modifications made by the previous owner. Finally, the silent blocks of the rear stabilizer bar could transmit vibrations in the trunk. Once the source is identified, the repair should be simple.

 

Thank you!

 

Update :

So I'm noticing this rattle mosrly happens when car is cold (like in morning) but as I use it ans day warms up, it mostly goes away.

 

I been experiencing this with my Z ever since it started getting cold. I hear it every time I pull out of the driveway in the morning. Once im driving I dont hear it anymore. Some of those suspension bushings are getting really old and may start squeaking.

 

As soon as you stsrt driving its gone ? I hear the rattle on bumps as long as its cold .

 

ill pay more attention again tomorrow morning when i leave to work. I hear right when im pulling out the driver way and for a little as im driving away from the house. After that to be honest I dont pay much attention but for sure by the time i get to work I dont hear at and I have to drive into the parking structure with speed bumps.

 

So I already responded to your previous post with the new Z and mentioning the most common sources of rear trunk rattles.

If you already addressed the more common causes I mentioned before, then there's a high probability it's the upper shock bushings for the rear struts. These are notorious for wearing out, there's also a cheap gasket from the factory that deteriorates overtime allowing for metal to metal contact between the shock mount and chassis. KYB sells a replacement shock bushing kit and I made a replacement gasket out of a 1mm thick sheet of silicone. This is a very easy task to DIY at home with basic tools.

Without sitting shotgun with you and listening to the noise myself, it's difficult to help further. There's always the chance of a loose item in the trunk that's fallen behind a panel or cover somewhere. To completely rule out the spare tire and roadside kit, I recommend pulling those items out of the car entirely and spending time driving without them. Hell even pull out the trunk carpet and false floor cover.

One noise I found very difficult to trace down was actually coming from my passenger seat rail cross-over wire, the one that interconnects the rail locks to the release lever, allowing the seat to slide forward and back. The seat's wire harness would occasionally vibrate (under the right resonance frequency) against the steel wire and make a very loud, but difficult to trace noise. I put some soft Tessa harness tape on the harness problem area and also wrapped the seat rail wire with some felt tape to resolve this issue. Initially, I thought the noise was coming from the passenger door or even the rear trunk area because of the way the sound was bouncing off the interior of the car. I'm not saying this is true for your case, but wanted to point out that interior noises can play tricks with your ears. It's always best to have a buddy in the car to help pinpoint the exact location.

Good Luck!
-Icer

 

Thank you!!!

I am really thinking it's the rear shock bushings. It has to be something that's either stiff or compressed when cold then expands or softens when it warms up, becuase it definatdly goes away when the car heats up a bit.

 

Maybe the gasket on the rear upper shock mount

 

Im honestly starting to think its jjst the entire suspension set needs to change. Too much creaking and rattling especially when it's cold.

Theres a reason the car looks brand new insids and out, and the dealer himself told me the car was mostly garaged since 2008 and only had 25k miles on it, and a side effect of that is im starting to think things like the rubber and springs and other parts thst need to be used constantly just get old due to age and lack of use.

I just don't know how much it would cost to replace entire suspension system. I just paid $600 for a busted rear differential bushing.

 

My 08 upper shock gaskets were toast when it was only 5 years old

 

Did that cause rattling pver bumps that seemed to come from the trunk area ? Mine feels like it's behind passnger side seat of the trunk area

 

why wouldnt it.. it mounts below the rear strut bar in the trunk, and top of the arch in the wheel well, hence it will make the sound come from that area

 

The ENTIRE suspension?

With quality parts? Probably a little over half what you paid for it.

Not too sure why you would want to replace everything... What a mod dilemma.

 

Thank you for the pic. Any way I can test this without having to raise the car?

My only thing is it rially doesn't sound like metal rattling. It sounds like plastic over plastic.

I just noticed this morning that this part squeaks and creaks when you press on it. It looks pretty tight but I can try to find a wrench and tighten it more.

 

I doubt your tail lights are the cause of the noise, as those live outside the hatch seal and are held tight when the hatch is closed. I wouldn't overtighten those either, you can easily break the plastic if you're not careful.

Have you checked your glove box behind the passenger seat? Also check the smaller compartments between the seats in the upper parcel shelf area (between the rear speakers). Make sure there's no loose items.

I did have a tapping sound that came from the B-pillar area, between the upper sill panel and lower panel where the seat belt routes. You can also sometimes get a tapping sound from the B-pillar cover that extends over the speaker house into the trunk area at the rear wheel house. Check around the rear wheel house, the quarter dome area isn't very well secured from the factory and can easily start rubbing/tapping adjacent panels.

Did you already address the tower brace plastics? The top 3 cover pieces are particularly bad from the factory (very loose), you can slide these around easily by hand.
Good Luck!
-Icer

 

I'll check all that again and hopefully I identify those parts correctly..not.sure what the tower braces are but I'll look.it up.

Also I didn't mean the brake lights and meant the black plastic piece with the screws in my pic. It squeaks when I press down on it but other side doesn't