DD_(in Germany)

The ambient temperature around these parts dropped to the low 40's (fahrenheit) about a week ago. Since that happened, I've noticed that when I start my car cold in the morning, I hear a strange metallic sound. It kind of sounds like there's someone 100-200 yards away that's using a grinder to cut stone, or one of those band saws for cutting wood. Somehow the sound seems to be far away but it's clearly coming from the engine.

The sound stops after about 30 seconds.

I'm thinking it could be something serious like things in the engine grinding (camshaft for example), or it might be just that the choke would be activated and the engine is revving higher and it might be just a metallic plate somewhere vibrating.

The noise doesn't bother me at all as such. What scares me is what it might be. I'm no expert like a lot of you here clearly are, but I know a fair number of noises and what they are (slipping fan belt, tappets, knocking, head gasket leak etc) but I've never heard a noise like this before ever (except when my neighbour 100yds away is cutting wood ;-).

I've checked my oil level (and even put in a litre a couple of days ago).

I threw up a video I made and put on youtube:

<a href="http://www.youtube.com/watch?v=Lfuo-p95rng"><img src="http://img529.imageshack.us/img529/5904/metallicsoundjz4.jpg" alt="click here to watch the short youtube video exhibiting this sound"></a>

ZCD2.7T

...only turns on when temps are low enough to require quicker heating of the catalyst to lower emissions.

Or at least that's what it sounds like to me.

Paracaidista2.7T

Because it happens on cold start, I would start it with the hood up and see if it is coming from the air pump at the center of the firewall.

newjerseyshorel

My biggest concern would be that your waterpump or a TBelt roller could be failing. If you had a bad bearing, it could sound like that. I'd say don't drive it until you get it figured out, or at least eliminate the possibility.

It's definitely a rotational sound. There are lots of things on the front of the motor that could produce those sounds. Besides the timing belt/water pump, it could be something on the serp belt, a fan, something with your cams, or maybe even turbos? If it's the turbo's that might explain why it sounds far away. I'm no turbo expert, but could it be a turbo starving for oil until the temp gets up?

Use your ear as best as you can, and track it down. Again, I'd avoid driving the car and even revving it until you are positive its not something to do with the tbelt.

I have a 2.8 so I'm not sure if thats what the secondary airpump sounds like on a 2.7t, but I've never heard that sound from my car.

JimmyC83

imagine a very large table saw sound cutting into wood. Its fine

DD_(in Germany)

Now I just have to figure out where the firewall and air pump is. I didn't know I had a firewall. Are there a lot of problems with people hacking into cars or sending trojans and worms into the engine? I didn't know I needed a firewall. Seriously though, I'll give that a listen in the morning

DD_(in Germany)

I only owned it for coming up on 2 months. I don't know if anything's been done other than the regular servicing. No idea if anything major has been replaced in its previous life.

It sounds like from waht ZCD2.7T and jimmyc83 said, it's not likely anything to worry about.

DD_(in Germany)

Now I just need a few days of warmish weather to confirm that it is just trying to warm up the cat faster. If I had some kind of space heater I could try warming up the garage for half an hour before next start, but I don't

The fact that I've had the car 2 months and it's only since the big drop in temperatures round here that this sound developed probably does lean in favour of what you guys have said.

If it was bearings, belts or anything else, then it would probably have happened prior to the temp drop. Last week when the temp was in the 60's there was nothing to be heard.

Audeye A6

OT: Is your grill painted? I like the black rather than the chrome.

paulroad

I have this under the same conditions as well. It is a DIY fix and not costly. I still let it sing as it works fine.