Cold start noise.

davidnSD

I just purchased this 2009 Impala and it makes the strangest high pitched winding noise when you first start the car when cold. Its almost sounds like some kind of little jet engine spinning up and once it warms up a little the thing begins to wind down and stop. It doesn't seem to be affecting the performance but it doesn't sound right to me. Can anyone else tell me if this is normal or something I should be concerned about. Dave

davidnSD

PS its a 2009 Impala LT 3.5 with 120k on it but it is in very good condition in almost every other way.

imidazol97

davidnSD said:

PS its a 2009 Impala LT 3.5 with 120k on it but it is in very good condition in almost every other way.

Can you locate it under the hood with your ears right after it's started?

I'd think of power steering pump, if it has hydraulic power steering still.
An idler pulley on the serpentine belt.
Another possibility might be a vacuum leak that closes some as the engine heats up. It may still be leaking, but the size of the opening and volume has changed so the sound is not created any longer.

Mr_Shiftright

I'd vote for a pulley bearing--not a big deal but I'd get on this sooner rather than later, so that something doesn't snap or seize. If you are VERY CAREFUL, you can buy a cheap "mechanic's stethoscope" at Autozone or some such and use the probe to better locate the noise.

davidnSD

Thanks, I will try getting a stethoscope and see if I can isolate the noise, I am thinking vacuum leak is a good possibility because the way it is so consistent in the way it starts and then stops. The power steering has a little wine to it that some fluid seems to have helped but i don't think that it. I was hoping maybe this was a common problem that some one had experienced but maybe not so much.

thecardoc3

Does the sound remind you of a small vacuum cleaner? If so then it might be normal. During start-up the secondary air pump runs to lean out the air/fuel ratio in the exhaust and also assist in getting the upstream catalytic convertor to light off.

imidazol97

Here's a video for a 2009 where he shows the location of the air pump on that year. I post the video only that it might help you locate the pump for when you listen for the source of the sound.

I wouldn't have thought of the secondary air pump because the air pump on my Cobalt 2008 sounds a little different from that. I has a delay after a cold start of half a minute or so but when it comes on it's more of a pumping sound and it quits after about 30 seconds or so. But I can see it has a vacuum cleaner sound now that
the Cardoc3 posted.

My Cobalt does not run the air pump on a cold start after sitting for short times during a cold winter day, at least not that I notice. But after a long overnight period where the engine coolant inside completely cools to garage temp 40-50 deg F, it does run. Same if it sits outside for hours on cold winter days not being driven after morning coffee until late afternoon or evening to put it in the garage, then I hear it running for 30 seconds or.

Does your car have a voltmeter? I start my Cobalt inside the garage and if I idle for a time, I see the headlights dim briefly and then brighten again when the current load of the secondary air pump kicks in. If your car shows that addition of a load when the sound starts, that might help tell you it's the normal operation of the air pump.

Good luck finding it and I hope it's something normal. Sounds like you have a good car there that will give you service for a long time with little maintenance.

If you determine what it is, please post here again to let me know.

imidazol97

https://www.youtube.com/watch?v=cwhNfJHdkNw

davidnSD

Thanks @imidazol97 I haven't verified this yet but Air pump was my first guess but I have never heard one that loud on start up. Since I am not getting a check engine light or code I am assuming the pump noise is somewhat normal. I will let you know when i can check it out better. Thanks again.

davidnSD

@thecardoc3 It does sound like an old style canister vacuum cleaner and it shuts down a few seconds before the cold idle shuts down so i think it is all related to cold start system engaging Thanks again