2001 with 42,000 on it. Only happens on ice cold start up (overnight). It sounds like a pump kicks on for 30 seconds or so and it has a bad bearing in it. That's the only way I can think to describe it.
I had the dealer check it and they said "it's normal" and it has something to do with a the catalytic converters getting air diverted to help them heat up. huh?[sm=dontgetit.gif]

Any ideas?

 

It is the Secondary Air Pump. It is a small belt driven pump that injects more air into the exhaust manifold to lean out the exhaust on a cold start until the cats get up to temp. The hose that feeds it is the small diameter hose that connects to the lower front inboard side of your air filter box. There have been a few that have pulled it out and lubed the bearings to quiet it down, but if you can live with the short duration noise why bother?

 

thanks XCLR8TT!! The service tech at the dealer wasn't real convincing, almost like he was making it up as he went along. Doesn't bother me much, just strange.

 

i thought the air pump was electric? and you should deal with the sound until it dies, otherwise you have to shell out 200 bucks for a new one.

 

Whoops... you are correct. It is an electric pump, for some reason I was thinking about the pump I've had on previous cars. Still does the same thing though.

 

secondary air pump is electric not belt driven and they do get noisy when weather is very cold basically its doing its job but can be annoying, if you think the noise is excessive then a new pump might be required

 

Anyone have a diagram or picture? Can the bearings be replaced or do you have to replace the whole unit?

 

i dont think you can replace the bearing in it, i definatly looks like a r and r part.

 

A couple guys on Audiworld have opened them up and cleaned/lubed the shaft to get it to quiet down.

 

My car did the same thing last night!
Scared the hell out of me, I can't cope with the idea of something being wrong with my TT. [:-]

Okay so I'll ask again.
What other strange noises or system lights can be expected from cold weather?