Unknown Underhood Chirp

**Spikito** · 12-18-2011, 02:49 PM

Ok so a few months back, i noticed that after my car got wet, it would squeal a little when I started it, seemed like the belt to me.

I replaced the main serpentine belt, but it didn't seem to really fix it. now it chirps all the time, its never a solid squeal, like a bad belt, just a real quick, short, chirp chirp chirp. I cant really tell if it chirps faster with higher RPMS because my exhaust covers it up.

Last night I got out of my car when i killed it and walked around in front of it, and noticed it was still chirping with the engine off, but the time between the chirps was much longer...and kept getting longer until it stopped completely, probably 10 seconds after I killed it.

My first thought was fans, but they don't come on with start up. It can't be accessories because they stop when the motor does.

Any ideas?

**Deviant LS1** · 12-19-2011, 07:02 AM

I had a similar issue. I would have a random belt squeak and I could hear it after I shut the car off. The belt squeak and the fan squeak were two separate issues. Try taking both the main belt and a/c belt off and turn all the pulleys. Then try and move both the a/c tensioner and the main belt tensioner and see if they're loose. Then put the A/C belt on and start the car. It will be okay to idle the car for a little while without the main belt to check and see if your A/C drive is the squeaking problem. If that's fine then take the a/c belt off and run the main belt and check for noise.

After being thoroughly frustrated and replacing all the idlers and main belt tensioner and both belts my squeak went away after replacing the a/c belt tensioner. I went through a couple sets of belts thinking they were going bad. With the new belts the squeak would go away for a few weeks and then come back. As the a/c belt stretched a bit the tensioner couldn't hold enough tension and the belt would squeak.

**Knight** · 12-19-2011, 07:29 AM

I agree with Deviant. I'd start with the belts and pulleys, as they're going to be the easiest and cheapest to check. Just a side thought, have you eliminated the secondary AIR pump? I have had them make some wierd noises. After that, I'd look towards the cooling system.

**pajeff02** · 12-19-2011, 08:37 AM

After the engine is off, the only possible sources would be the fans -- either cooling, HVAC or secondary air. The secondary air system only runs for a short time on cold startup, so it shouldn't be that. The HVAC fan would be more noticeable in the cabin than at the front of the car. This leaves the cooling fans as the most likely culprit.

**tatertot91** · 12-19-2011, 09:49 AM

Sounds like fans to me

**Smittro** · 12-19-2011, 01:07 PM

I would say the fans also.

Or the coolant bypass cap (radiator cap) is starting to stick and restricting coolant flow between the rad and rez possibly causeing the noise as cooling system presure bleeds down.

Also could be a vapor canister purge solinoid issue starting.

**pajeff02** · 12-19-2011, 01:20 PM

^^ Good thought. Those would also be a regular interval kind of noise that fades out like the OP described.

**Knight** · 12-19-2011, 03:14 PM

Exactly what I was thinking. I've never had them cause quite that noise before, but I definately wouldn't rule them out.

**Spikito** · 12-20-2011, 05:48 AM

AIR is deleted

barely audible in the car, loud under the hood

I played with it yesterday, and it was stopping as soon as the engine was killed this time, i tried revving manually to see if that increased the speed of the chirp, but my exhaust covered up the sound still.

i tried using a little piece of pipe to out tension on the main belt while it was spinning....better in theory than in practice, but in the end, didn't seem to help.

Based on what I've seen, and what yall have said, i think A/C belt tensioner is my most likely culprit, I stay away from A/C stuff, I didnt even know there was such a part...so ill start there.

**tatertot91** · 12-20-2011, 06:04 AM

Have you looked at the fans yet? Seems more likely if it keeps going after the engine shuts down

**Spikito** · 12-21-2011, 02:01 PM

Well I only noticed that once, and the fans wouldn't come on right away during a cold start, like its been doing, and the tone DOES change with higher RPMs.

**tatertot91** · 12-22-2011, 08:29 AM

Pull the ac belt off the car and see if the noise goes away.

**Spikito** · 12-22-2011, 08:42 AM

Ill get it checked out if itll ever quit being 40 degrees and rainy...i hate december in Texas

**SSwt00SS** · 12-27-2011, 06:42 AM

consider the A/C idler pulley. thats the one that was squeaking on my '99 Formula that ended up getting replaced. not the tensioner pulley in my case.

**kenro23** · 12-27-2011, 07:00 AM

I had the same issue and changed every belt pulley and tensioner and couldnt find the noise. It ended up being the a/c bracket. Sounds crazy still to me but the bracket that holds the a/c on was bent somehow. Been perfectly fine since then

**pajeff02** · 12-27-2011, 07:03 AM

^^ That is very strange.

**kenro23** · 12-27-2011, 07:06 AM

Yes it is. How would that even become bent?

**kenro23** · 12-27-2011, 07:35 AM

But after changing all that i changed and the noise was still there, I took it to a mechanic that mainly works on f-bodies and he pulled it off and one from another car and noticed it.

**wileyCoyote** · 12-29-2011, 10:33 AM

i'd suspect this is a TSB problem from way back.. there was a TSB that called for replacing an idler pulley and bracket, ..some kinda GM defect in the design, would cause a chirp-chirp-chirp, mainly noticeable at idle... do a quick search for "double row idler pulley TSB" or something like that...