Ferocity02

iTrader: (60)

I've noticed in the last couple weeks that when I turn the engine off, for about two seconds, I can hear a hissing coming from the engine bay. I can hear it from inside the car so it's sorta loud. It sounds almost exactly like air escaping from a tire. At first it's fast, but then it slows down and stops to where there is no pressure. It's not the tire though, and it only last like 2 seconds. I was thinking maybe it's a radiator, not sure though. Anyone care to explain? Thanks!

WILWAXU

iTrader: (6)

More than likely compression moving by a partially closed valve.

Ferocity02

iTrader: (60)

Possibly, but I hear it EVERY time and it always sounds the EXACT same. I would think that the engine doesn't stop the same way every time.

BYBYC5

air pump maybe, mind did this and i tore my hair out looking for it but gave up, but after i deleted the pump, and quite a few other things its stopped, just a thought

M3EATER

It's the AIR pump system.

Gordon

Z-Rated

I thought it was AC?

1RawTA

iTrader: (1)

It is most likely that air pump or ac, but also check the lid on the radiator is tight, i had that problem once, the cap was 100% tight and i heard lots of hissing when the car was turned off

Gev

Air Pump or AC.

Colonel

Radiator or AC.

Smoke_Ford

AC man.

Turo

iTrader: (23)

my A/C does that

Ferocity02

iTrader: (60)

Will the A/C make the noise even if it's off? I never use it

TA Dave

A large Snake? Have you raced a Cobra lately?

A/C or cooling system.

felton316

AC, cause I get the same noise and I don't have AIR system anymore.

DONAIMIAN

iTrader: (18)

To me its normal. I hear it on every LS1 with a lid.

Danny2tek

iTrader: (1)

A/C

SmaknaSS

iTrader: (1)

I would check the hose between the intake and brake booster.

blk~2000~Z28

I have that same sound. I never noticed it until after I installed my SLP lid with the rubber block-off strip in front. I am not 100% sure, but seeing as how I only noticed it after I installed those parts has led me to believe that it was that. I also rarely ever use A/C and I know what the AIR pump sounds on startup at least. If you have a lid and that little rubber strip you should try removing the strip and listening. Next time unplug your AIR pump. Next time unplug your A/C. Radiator? That should help you find the problem or get you a lot of SES codes .

quickWS6

NO A/C or AIR here, and mine does it. Mine kinda whistles all the time though from the lid.

Ferocity02

iTrader: (60)

Ok.... I'm sure it's not the lid, because I hear the hissing after I turn the ignition off. The engine has stopped turning and then I hear the hissing noise for 2-3 seconds after the engine has stopped rotating. I never use the A/C, I do have the AIR pump but doesn't that make more of a whining noise?