knocking sound after engine shuts off...???

[MS3 GT]

Dose anybody got this issue like me?? i've been noticed that i have had heard some knocking noise after i shut 0ff my engine..what was that noise?it sounds like the pistons is hitting the enigne wall...??or a part of engine is hitting the metal body chasics..??also i smelled some bad shit from the intake pipe where u see it when u poped the hood. i look through the hole on the intake pipe where u c the MAF sensor. all these gray ashes were all in the pipe?? its brand new car only 5k miles on it..!!i believe it happened after the INJEN CAI installed..with that knocking sound....!!!

[mazdaspeedkid]

i hear the same thing too. if i go on a long hard drive but if i take it easy i dont. its 50/50 i would want to know also on this.

[NCZ13]

relax its your cats cooling down.

metal expands as it gets hot. the metal is "shrinking" when it cools, therefore it makes clicking sounds

[stars.eg6]

relax its your cats cooling down.

metal expands as it gets hot. the metal is "shrinking" when it cools, therefore it makes clicking sounds

what if we are catless?

[Coolfactor]

I also have that knocking noise when shutting down the engine.. and it's not the cats trust me. Mine does it intermittently and when it does, I hear a sequence of 7-8 quick knocking sounds as if, like MS3 GT described, the pistons where hitting the wall.. metal-to-metal type of noise. I also suspect the pulleys or tensioner.. seems to be coming from that area anyways.