: Mechinical buzzing noise from under hood ( 2002 Deville, 150,000)

02-18-14, 01:50 PM
I have a hearing loss, so I am trying to figure out what people are trying to tell me.

They tell me there is a power saw noise (like a mechanical buzz) for about 30 seconds after I start the engine. It is coming from under the hood. I asked then to try tell me where it is coming from. One person said behind the engine near the firewall, the other person said it sounds close to the PCM over near the air filter. Everyone is 95% sure it is something OUTSIDE of the engine.

There is no CEL and the engine runs fine.

I did some tests and here are the results.

1) It ONLY makes this noise on a cold start (engine is under 60 degrees) for about 30 seconds. Once the sound stops, it doesn't come back until the engine has cooled off (and only when I start the engine). Also, when I start the engine, then turn it off after say 5 seconds, they can hear the buzz "whine down" (almost like a spinning noise slowing down).

2) When I start the engine and press on the gas pedal and let off several times, that "mechanical buzz" does not change. So this says it is not part of the engine. I know it is not the cooling fans, since they are not spinning and not the blower motor, since I turned it off.

3) When I am watching the RPM on the dashboard, when it is cold, I start the engine and the RPM is about 1100. The people tell me there is a buzz, BUT when they raise their hand to tell me the Buzz stopped, the RPM immediately drop to 700. So, is there something that makes make this noise when the engine is trying to warm up for about 30 seconds?
is this normal noise?

Any other ideas ?


02-18-14, 02:28 PM
It's the A.I.R. pump. The A.I.R. system pumps fresh air into the cat at cold start to help it reach operating temp more quickly.

Either the pump cover has come off (common), or the pump is failing and making a noise it shouldn't be. You'll have to remove the plastic air deflector under the radiator to see the pump. It's in front of the drivers side wheel.

02-18-14, 03:19 PM


#17 in this view

02-19-14, 09:09 AM
This is starting to make sense. I remember putting the car up on the ramp, and the people said it seems louder under the car, but still could not locate it. Maybe it was because the deflector was in the way.

THANKS !! I will take a look at this!!

02-19-14, 04:07 PM
When looking on the internet, sometimes I see it says "AIR pump left and AIR pump right". Does mine only have one pump or two? O'Reilys has one for about $240. Is there another option to buy a cheaper one on the internet? which sites do you recommend for buying OEM and NEW Cadillac parts?

02-19-14, 04:56 PM
Look on the right hand strut tower. There will be one, two, or no gray relays clipped to a bracket there.

Always talk to Chris in parts at Rippy Cadillac - Authorized Vendors forum ^^^ or over there >>>

www.rockauto.com is another reliable parts source. www.gmpartsgiant.com is good, but they make it up on shipping "costs".

02-19-14, 05:01 PM
When looking on the internet, sometimes I see it says "AIR pump left and AIR pump right". Does mine only have one pump or two? O'Reilys has one for about $240. Is there another option to buy a cheaper one on the internet? which sites do you recommend for buying OEM and NEW Cadillac parts?

WOAH, that's overpriced!

Yeah, call Chris, tell him you're a forum member.

02-20-14, 12:46 PM
Glad to hear that $240 is "overpriced"! Will e-mail Chris, after I can confirm the AIR pump is making the noise.

By the way, can someone briefly explain what this pump does? does it ONLY come on when you start the car cold? or does the pump come on under certain conditions? Does the pump come on while you are driving on the highway, idling, etc.. ?

If the pump grinds apart, what happens? Will it ruin the engine?

02-20-14, 02:32 PM
It's more of a blower than a pump. It blows fresh air into the exhaust to lite the CAT quicker, that is, bring it up to operating temp quicker, thus reducing the time that the CAT is unproductive (first 40 seconds of a cold start). All this to satisfy the tree huggers.

If it falls apart and stops working the air quality police will prosecute you to the fullest extent of the law (life in prison breathing unfiltered air). Oh yeah, your MIL will come on, store a DTC and you cannot pass an emissions test. Other than that, neither you nor your car will no that it is inop.

I am not subjected to emissions testing so if there was a way to bypass the MIL, I never would have replaced mine.

09-15-15, 01:33 PM
Sorry to bring this back, but I got a P410 code, and was surprised it came on WHILE I was driving on the highway for 30 minutes! It shows P410 and that is related to AIR pump. I was looking at RockAuto and there are 3 choices. DO i need a new bracket or not? In other words if it is made of metal, I assume I can reuse the old one. Or should I just replace everything? See options below...

ACDELCO 19260940 GM Original Equipment; Does Not Include Bracket $120.89

ACDELCO 19303240 {#19515548, 215617} GM Original Equipment; Improved Design with Revised Inlet Hose $203.79


Also, this doesn't look that hard to replace. Maybe 2 hours? Am I correct?