Ok so i get this nasty metal on metal clanging sound from time to time. It sounds like its coming from the bottom of the engine compartment. I was told that it's possibly the AC compressor cluch bearings? May hear it when defrost is on? I feel like it happens mainly when I start the vehicle. Any advice would be great, sounds like sh!t and worries me. Last 1.5 years I've had to put alot of $ for maintenance into this car, seems more than its worth, but right now a new car isn't really an option. Please let me know if you can help diagnose this problem based on what I've said.

Thanks,
99 Z24 129,000 Miles

Forgot to mention. This problem had occurred 3 months ago and then went away? It's unfortuanetly back. Suggestions/help would be awesome guys, THANKS!

it sound like ur timing chain my car was doing the same thing it started with the noise then it went away and came bac and a coupel of weeks later my car jumped time

Thanks Jonathan. If that is the case how serious is it? What has to be done to be fixed, time/parts cost? Also I drove the car today and there was no noise..? More comments and suggestions would be great, thanks guys.

I have this happen , it should be be the bearing in the AC compressor. Its all one piece so you have to swap the whole thing out...

to fix it u just have to replace the tensoner or just replace the hole timing chain and everything .as far as fixing it i just pulled the moter because u have to take a cover off and its hard to do it with the moter in the car there is not a lot of room to get any tools in there .what moter and year is your car

JZ thanks, if this is the problem what am I looking at in parts & labor? Jonathan my car is a 99 Z24 2.4L. Is there any advice you guys can give me to pinpoint the issue?

The timing chain sucks to replace.

If for some reason it's you A/C compressor, just crawl under the car and unplug the electrical connector going to the compressor, if it's the compressor clutch making the noise it will never do it again unplugged but your A/c wont work either. You'll know that way though, and if it is you can fix it.

Mine does it sometimes - it will clank then I turn on the A/C and it goes away. It's kind of embarrassing when it does it.

Ok so its been 4 days since i posted this and I havent heard the noise or had any isssues. I know it will unfortunately come back but i still haven't pinpointed what it is.. Any othher help would be great, thanks.

If its going away then coming back it has to be ur ac compressor clutch. thats normal for them to do to the point that it just keeps screaming then eventually locks up.

when it starts doing it again take your serpentine belt off and see if it goes away. if it doesnt its you timing chain if it does check each pully turn the car off and wiggle and spin each pully if a bearing is bad in any of the pullys you will feel the roughness as you spin it and if theres play in any of the pully theyre bad. also check ac clutch grab it and turn it shouldnt be realy easy but turn it and see if you feel any roughness. the timing chain isnt really that hard just time consuming. not saying its easy but its easier than some . good luck

Does the sound go away when you turn the a/c on?
If it does, there is an adjustment/alignment GM can do and that will fix the issue.
I had it done 2 years ago and the sound has yet to come back.

Let me know

I drove the car friday and saturday night and the sound has yet to return?? I appreciate the comments but I feel like diagnosing it is an issue because I have little mechanical knowledge and there is currently no sound? If the sound happens again can I do what Weeble says and uplug it while the car is running?

To all those that can help: So the car made the noise when I started it today and lasted for about 20 seconds then went away. This is the first time it has came back since the original post which was 15 days ago. Does the compressor clutch spin when the car starts? The ac fan was off when I started it which is why I'm asking. Would like to properly diagnose this problem so i can take care of it before it really becomes an issue. Please help, thanks everyone!

Yes the clutch does spin since its connected to ur belt. if it came and went its almost 100% ur ac clutch. im finding that info for u now.

hey. what motor is in it? 2.2 or 2.4? clutch wont spin if the ac is off. take a screw driver or anything long and metal or a broom handle works to. or a mechanic stethascope. and listen to the pulleys all of them. if you notice one that sound alot diferent and sounds like crap like grinding. that pully is your problem. you can also take the belt off and spin them freely with your hand the revolution of the pully should be smooth no roughness at all should have some resistance but smooth resistance. if that all checks out an your sure it that side of the motor take the broom handle or screw driver and listen to timing chain from the the timing cover you shouldnt here any racket just a whirrling noise. what would really help is take a video of the noise and post it on her or youtube even if the noise isnt there. maybe we can notice a noise or something that your over looking. let me know

it does spin but its not engaged without the ac on. just the pully is engaged if that makes sense.

Opps, I just re-read what I typed. I ment to say the clutch PULLEY spins, but not the clutch itself. Im still willing to bet its the clutch since my girls vert does the exact same thing.

Does the sound go away if you turn the a/c on?
If it does, there is an adjustment GM can do to fix the issue, you don't need to replace the a/c clutch.

This happened to my 96 Sunfire 2 years ago, usually the sound would happen in damp weather.

Not reading through the comments so idk if anyone said this, since you said it went away 3 months ago and just came back, thats leading me to think its not your timing chain
Check if the noise goes away with the A/C on, when it's making the noise, take a long screw driver put it on the A/c and put the handle on your ear, you'll hear everything much louder and you can pin point the noise from there