I have an 04 G35 Coupe 5AT. Bought it used a year ago. I noticed a rattle from the engine bay - very faint. I thought it may be belt related. The car has 60k miles and was due for the a lot of maintenance. To date, I've flush the xmission, changed oil, brakes and plugs. Haven't done the belts yet.

At any rate, over the last few months the rattle has gotten worse. It is very noticeable - not so much from the top area of the engine - but is very noticeable from underneath the car. Seems loudest in the exhaust area around the engine.

Has anyone had a problem similar to this - or have any ideas as to what might be causing the rattle sound?

Thanks in advance for the help.

 

Any help? Could it be the catalytic converter? The car only has 60k miles. I don't think it's the valves. I would be able to hear the rattle from the top side of the engine bay - at least I would think this.

Might need to take to the dealer.

 

you want us to diagnose a SOUND from very little information. You'll have to be more detail.

WHen does it happen? What kind of rattle? does it change with throttle (increase/decrease)? Does it go away when hot, or is it non-existent when cold?

Cat heat shields can rattle. Anything not secure can rattle. Depending on what a "rattle" sounds like to you, you can have plenty of other things.

 

All at idle:
Engine cold, there is no rattle. After idling for 10mins or so, there is a slight rattle that is only noticeable underneath the car. If I drive the car aggressively for 10mins, then park the noise is noticeably louder. The idle rpm is roughly 800-850 rpm.

When the engine is revved in Park, the rattle speeds up and then gets drowned out by engine noise.

When I shift to drive, the rattle goes away. However, the rpm lowers to about 650rpm. While driving the car normally, I don't notice a rattle at all.

Is there a way to post or link an audio file?

 

The rattle is very consistent when the engine is hot. I initially thought it might be in the engine - a valve tick. But, the sound is almost not noticeable from the top-side of the engine bay. If it were a valve issue, I would think I could hear it more from the top-side.

I suppose it is possible that something worked lose, but I would think that if something were lose, I would hear it regardless of whether the engine was hot or cold.

Thanks for the help.

 

Oil levels are good? You need to watch for oil consumption if you aren't.

You can post a video. You will need to use a hosting site such as photobucket. There are many site you can use.

 

<embed width="600" height="361" type="application/x-shockwave-flash" allowfullscreen="true" allowscriptaccess="always" wmode="transparent" src="http://static.photobucket.com/player.swf?file=http://vid810.photobucket.com/albums/zz30/jjsomer/Car Rattle/VID00000.flv">

Hopefully the sound quality is good enough. The last 30 seconds is from underneath the car right behind the front wheels.