I know every cobalt owner knows what I'm talking about, your parked or sitting at light or something and you hear a tap tap tap noise come from the trunk area, Im curious what it is does anyone know?

 

A monkey!!!!! or was it that bum on the corner???

I have not had that problem with mine while sitting still.

One possible thing is the parking brake adjusting itself. Other than that, I am not sure.

 

Fuel pump!
its normal.

 

I've never heard a fuel pump make a knock knock knock sound before, why would it do that? On some cars you can actually hear them running if they are loud enough but other then that I've never heard of or came across one that made a tapping sound or knocking sound at random times.

The parking brake doesn't make noise while self adjusting. Theres no motor or anything that would cause an audible noise.

 

Its a cobalt thing? idk It would some times happen to me when shutting the car off I would hear a tap tap tap, Local tuners/car club said its the fuel pump and its normal.

 

It's the evil troll hiding in your trunk trying to get out.

 

i actually heard its the antenna testing itself or something, sounds like someone's tapping on your back window lol i know exactly what ur talking about

 

Man I always wondered what that was. Finally I can sleep easy at night.

 

^ YES I really though I was losing it when I first heard it, I thought I had a raccoon or something, somewhere in a body panel

 

The antenna on my LT has no motor or anything how and why would an antenna "test" itself?

 

^x2 no model balt has a motor its a fixed unit

 

neither does mine lol, i heard that is what it was on a post on here a while back not sure if that is right but just giving you guys a possible explaniation of what it could be

 

You were close kinda lol
https://www.cobaltss.net/forums/2-0l...k-knock-10295/
"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)."

 

I was never sure, but did sound like it was coming from under the car like right behind the rear seat. I checked the trunk for rattles and found nothing. Then when I had it down with less gas, aka not full, it seemed to happen more. Thats what made me guess it was the fuel related, but its nice to be sure.

 

Ok I figured exactly that, it had something to do with the EVAP thats all I wanted to know thank you.

 

lol i kinda was close

 

Somewhee in here a ling time ago someone said it was the trunk doing some kind of self test. That's what it sounds like to me. It doesn't always happen right after you turn your car off. Hmn....

 

LOL this was bothering me for sometime! Im glad its normal!

 

most likely a bound and gagged hooker in the trunk, happens to me all the time.

 

lol my friends are like wtf was that lol im like idk but its normal. they be like is some in the tunk?

 

lol im glade im not the only one havin this problem it scared the hell out of me one night i got in my car after work i was like who the hell is bangin on my car lmao...

 

lol the joys of owning a cobalt

 

its the wonderful evap system.

 

the lil asian girl you thought was dead when you put her in the trunk isnt.

 

i never even thought twice about this until i read this