Knock Knock Knock!
 

Anyone here ever hear knocking coming from the back of there Cobalt ss/sc. I hear it sometimes even when the car has just been parked and the engine is shut off. It sounds like someone is knocking on the side of the car?? Very strange.

yeah my car does this too. mine sounds like its coming from the muffler area. weird.

yeah it just happened to me about an hour ago while i was messing with my radio stations. it has happened plenty of times before that although i have no clue what it is... first time freaked me out cause it was at night.

HAHAHA yeah the first time it did it to me was at night too out in the country....freaked me out!

I get that too. It knocks 2 to 3 times and it's gone until I shut the car off and wait over night and start it back up in the morning. What the hell is that? I thought it was only my car. I think GM included a ghost in our cars for no extra cost.

mine clicks whenever i shut it off, get out, lock it, and got inside... im thinking it is just the engine and supercharger cooling down...

It's not clicking. It's knocking as if someone outside came up to my car and started knocking on my car. It comes from the right rear of the car on mine.

its probably one of two things....

If it is a pingy sound it could be the exhaust cooling down. The other option is the trunk latch checking itself.

I don't think it's either one. I can't imagine the trunk latch making this sound and the pingy sound isn't what it is.

dang i thoughtt his was going to be a knock knock joke. but anyways. mine does it to. mostly in drive threws

I'm telling you it's a GHOST. Don't belive me? Check this out http://www.princeton.edu/~ccaro/mist_or_ghost2.html

lol...thats good.

i get a :redx: for that link

You need quicktime I belive to view the file. It's pretty creepy if you ask me.

I prolly is a ghost, the Ghost of GM Employee Discount for everyone event pricing...

How about the gas in the gas tank moving around. My cavalier was really bad for this. Every time you were around 3/4 tank you would hear the gas move around?

Just another idea?

The best way I can describe it is to have someone knock on the right rear of your car lightly. It will sound almost exactly like that. I'm not worried about it I just want to know what the hell it is. I get it like once a week.

When you hear it try to keep a mental record of how much gas you have. If it is always somewhat around full area when it does it. Most likely it will be the gas moving. :)

Yeah I remember looking once and my gas was about 3/4 to full when it happened. I'll look at the guage next time. Idk it just freaks me out, especially if it's like 2 in the morning and it's really quiet out. (as you can see, i'm afraid of the dark lol)

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.

Yes i think it is the gas moving, mine freaked me out the first time i heard it, but then i noticed it was the gas.

Ah yes the infamous Cobalt Ghost, I have yet to find out where it is coming from.... I will find it some day...

I was told the same thing by my service guy at the dealership. I've had that noise to so while I was at their shop putting a windshield in one of their SSR's, I happened to catch him and ask, he said it was the same thing.

:twothumbs Yes, I know nothing! :lol: j/k

I still think it was a ghost...

It is the computer checking to see if the trunk is locked. It cycles about 3 times (3 Knocking noises). And also when you turn the car off something in the engine bay ( something to do with the s/c), it almost sounds like dropping a marble into a plastic cup.

EDIT: Disregaurd the trunk thing LOL!

thats happening to me too, i just noticed yesterday.

dude laugh @ me all you want but my car did the same thing....CHECK YOUR RADIO ANTENNA .....mine constantly comes loose for one reason or another and wobbles, when it does that (even in the slightest wind or wiggle in the car) it will make a clunk or "Knock" noise...try it!

i was on an 1/8 of a tank when it happened

the same thing happens to me all the damn time.

and im glad to know that the knock knock knock is not a ghost....b/c it scares teh shit outta me

OK, look! I'm at work and just brought my SS/SC in to the shop. I commanded the EVAP vent soliniod On and Off. Guess what? Same noise, it is the EVAP system, trust me.

mine does the same also

Lol this is good.

I get a weird ticking noise in my car. Its from the headers/downpipe. Its just that type of metal cooling down. My parents new Yukon does the same thing when it cools down. Sounds more like water dripping on metal.

It's not gas moving around in the tank, my Saturn does that so I'm familiar with that sound. Mine has the knock also, like others I first heard it at night after getting home from work, freaked me out. I don't think it's the exhaust because it still does it after installing my Corsa system and it sounds the same.

Well I am glad I wasn't the only one hearing this, will see what the dealer says on my next oil change!

watch a lot of horror movies do we,lol, if i remember right from other threads/posts, it is either the fuel pump or the trunk latch checking itself

listen to NJBLUESS . I as well work for a gm dealership and it is true what he says. command the vent solenoid on and off with the scan tool and the same noise is heard. it's not a ghost, it's not the trunk latch, IT'S THE EVAP SYSTEM DOING A SELF TEST!!

Mine does this ALOT.....several times in a single drive sometimes, I can't see the EVAP system testing itself THIS often....Then again I'm no mechanic, but I do like the loose antenna idea....

It's just your trunk monkey. HAHAHA

I get the knocking sounds too. Usaully while stationary.

I thought it was the fuel pump/system .