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 **** 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 .

 

Mine did this a day later after I installed my Sportlines on her. At first, I couldn't figure out what the heck it was. It sounded like a loose suspension member towards the rear of the car. I was thinking I forgot to put a bolt back on when I put her back together, but I only heard it after I came to a complete stop or from a slight 2 mph roll.

My friend (EVO04) told me to check the antenna, and sure enough that's what it was alright. I was almost ready to take it back to the dealership.

The EVAP thing is a different noise altogether. I get it when I pull into my garage about 3 to 5 seconds after I shut her off. That sounds correct that the EVAP would cycle like that. It is weird sounding though.

 

when my mother got her new cougarC2, me and my dad drove to granny, it was dark, and it made like a low dog barking sound after we shut it down and we thought we hit granny's dog. lmao but it is the trunk latch....just thought i would share that with u

 

Scaredy cats are we??

Just kidding.

 

So did I. But a Knock Knock joke is usually 2 Knocks, not 3.