I noticed today that early in the morning when the engine is still cool (presumably) I hear a clunk or pop noise. Very similar to the sound a rock or branch makes as it pops up into your car. This happens only at a stop light in neutral when I don't have my foot on the clutch.

It sounds like it's coming from behind me, my only guess right now is either the brakes (as that's the only thing I'm holding at the time) or there's something wrong with the engine at idle.

Any ideas, things to suggest when I take it in to the dealer for service this week?

 

Hmm...do you feel anything, or just hear it? Maybe a sticking caliper, misfire, etc...hard to diagnose that noise. If you're seriously concerned, take it in. I haven't seen anyone else post anything similar to base it off of.

 

I can't remember the exact details but its something to do with suspension being "purged" to the atmosphere... a tech on here stated without it we would have a lot more problems with our cars in that department...

Its like someone is tapping on your wing or back window... when I first got my car in 05 it tripped me out a couple of times... WHO'S THERE?!?!


-Brad


EDIT POST **update**
I found the original thread i was referring to...

Per NJBLUESS

I've posted about this," knock- knock- knock", noise before and was blown off! The EVAP system is testing itself! The noise is from a soloniod being energized by the PCM. EVAP system tests run under certain conditions. The tests will occur shortly after start up and just after shut down. The soloniod is activated to relieve vacuum in the fuel tank after it checked for leaks. (leave you fuel cap loose and see what happens).
But, I do like the ghost story.


Thread
https://www.cobaltss.net/forums/show...ght=Clunk+stop

thx.

 

Alot of cobalts in general seem to have that same noise.I would hear that noise when i drove the car around and would park it and turn the car off.Yeah what ProJecTX said.

 

It's probably transmission related. I get tranny clunk but everything is fine. (redline not tc)

 

Wow, thanks for pointing that out, I did a search and didn't see that thread. This allays my concern quite a bit.

It is the same exact noise after the car is shut off as well. I'm still going to get it looked at either way. I'm going to the dealer no matter what.

 

it also does it with the car off. it's called the "phantom knock" and it is exactly what you're describing, it sounds like someone is tapping on your car, you turn around, and no one is there. totally normal. all cobalts do it, and it's been discussed to death for years. take a look through some old posts. this w3ay you'll save yourself a trip to the dealer for something that's 100% normal.

 

Mine does it randomly. It sounds like someone is tapping on your trunklid. It did it this morning actually when I got to school and turned the car off. It doesn't bother me.

 

I swear that's what I used to hear in my '98 Cavalier Z24 before I bought my 08 TC. I had no idea what it was until now. Anybody know if that's what I was hearing? I've never heard it in my Cobalt though.

 

Isn't this where the trunk is checking to see if its closed or something of the sort? My ss/sc did this all the time after the car was turned off.