hello everyone I'm new to this, I had a quick question and need someone's best mechanical advice on what the problem could be, how much it could cost, and if it's a problem that needs too be fixed right away, and should I reduce driving the car,

I'm gonna try and give as much information as I can and if you need more please ask...

The car is a 2003 Porsche 911 Cabriolet with 144k miles. Everything is pretty much bone stock besides the exhaust system. The previous owner put a "fab speed" set up on it.. Which made the check engine light on, The problem I'm having is I started noticing a strange noise coming from under the rear hood, I'm gonna say it's been there for about a month but haven't payed much attention to it until last week. It sounds like it is coming from the serpentine belt or alternator, well at least that's where it's at its loudest, the only way I can describe what kind of noise it sounds like is like a "Tin can" rattling, grinding, of some sort, from inside the car it is just as loud from hearing it with the hood open. Only difference is it sounds more like a grinding, rather than a rattling tin can.. I noticed that when I rev alittle above 1500 rpm is goes silent but then comes back after I stop revving, I also noticed it gets like 50% quiter when I turn the AC or Heat on... Like i explained earlier due to the fact it sounds like a rattling/grinding tin can. It's not one continuous noise/pitch or whatever you wanna call it, like a knock in the motor for example. It's one continuous clack-clack-clack noise doesn't get any louder or lower... In my case it differences .. Like some times Itll get louder for a split second, than rattle lower, ect... From what I'm hearing it really sounds like to me something broke off SOMEWHERE. I'm assuming in the alternator or belt and is now rattling or grinding around.... I really tried my best too explain. But if you still have no clue what I'm saying (which I don't blame you) lol I recorded a video of it which is posted below.... I don't think it is an ims problem because if it was the car would've died a month ago..

 

 

is that fluids on the snorkel & airbox? Could be your water pump?

 

No it is rain.

 

Take off the serpentine belt and run the motor for a bit. That should let you know if idle pulley/alt/waterpump or if motor.

Then from there figure out what is the offending accessory: PS pump, Alt, AC, etc....

 

It is always best when making a video to keep your frickin' hand from in front of the lens!

And hold the camera still so one can try to get a sense of which direction the noise is coming from.

Anyhow, the noise sounds external to the engine so that pretty much leaves the accessory drive as the source.

I would second what B8_RDC had to offer and remove the belt. Be sure to note its routing and direction of rotation in case you intend to re-install it.

Check the belt. If it has sharp edges that's a good sign the belt is rubbing and it rubs because an accessory drive has too much free play in its bearings.

Start the engine and let it run and verify the noise is still present or if it is absent. If it is still present shut off the engine and button things up. You are done. Flat bed the car to a shop for a pro's diagnosis.

If the noise is gone then an accessory drive is most likely to blame. Give all of them a wiggle checking for play. You have a number to test so the one with the most play is the culprit.

It the noise is coming from an accessory drive my money -- but not much... -- is on the water pump.

 

Any update here would be appreciated?

 

The exhaust heat shield rattling sounds like a tin can rattling.