Buzzing Sound

[Wausau 911]

'04 C2 garage kept- but temps been in the high 20's in there, run the car every couple days and on startup, hear a buzzing sound coming from engine compartment. Goes away after about 45 seconds. New serpentine belt. Anyone have any ideas what could be making this sound? Replies appreciated. Thx

[Loren]

Sounds like a noisy air injection pump.

Open the lid and check it - it is next to the coolant tank on the left side.

[kgoertz]

It is likely the "secondary air injection pump". It runs briefly at startup and the pump is known to whine when it is too dirty. The pump is near the left rear of the engine compartment right beside the coolant reservoir.

The pump is quite expensive but a very easy DIY to replace. Search for SAI.

Also many here (including myself) have had success by removing the pump, re-greasing the bearings, and blowing the dust out of the pump with an air compressor. There are instructions on this forum. I cleaned mine over a year ago and the buzzing sound has not returned yet.

[Ronnie38]

Ditto on that, had that problem on my Z3M, re-lubing worked for 3 years, then a bearing froze so I had to replace it.

[Wausau 911]

Thx for all the input, I'll check in the morning

[kbrandsma]

Not recommended to let car run at idle to warm up. Hard to tell from your post, but always better to drive vehicle upon starting and allow all fluids to warm with vehicle in motion and according to manual, best not to exceed 4200 RPM until temp is up to operating temperature, about 170+ degrees(or 5 minutes) or so,

Edited February 19, 2014 by kbrandsma

[Wausau 911]

Thx for the above post, guess I should read the manual more closely.

Anyway, put my ear closer to the engine and the sound isn't coming from the pump, sounds more like it coming from the center, maybe alternator or a pulley.