WS6_2000

I have a 2000 Trans Am with Headers and X Rumbler exhaust. I disconnected the EGR valve from the headers and plugged the hole in the intake manifold. The other day I started to notice that when I shut the engine off I hear a hissing noise, fairly loud, and Im not sure what it is. I dont remember it happening before but maybe it has always been there. Anyone have any ideas?

whytryz28

iTrader: (28)

I have the same hissing noise at shut off, its coming from my lid, i guess its the engine sucking the air very slowly still.

DarkCloud

make sure the hole in the intake is plugged good. when i got my blockoff plate, it didnt seal right the first time around, and i used to hear a hissing noise comming from there...

TORCHD 02 TA

iTrader: (39)

It is your A.I.R. Pump.. you can take it out, but you will need to tune it out or you will throw a SES

94'BLKBRD

iTrader: (76)

The hissing noise youre hearing is from the lid.

9000th01ss

iTrader: (10)

Everyone needs to re-read. The intake, the lid, nothings going to hiss with the engine off.
Does it have AC? It's usually the AC, refrigerant equalizing through the orifice tube when shut off.

94'BLKBRD

iTrader: (76)

my car hisses everytime I shut off the engine.

ae13291

iTrader: (8)

spray brake cleaner around the egr hole with the car started, if the engine idle changes then there u go. it may be leaking around there.

02WS6_TA

iTrader: (1)

X2, My car done the same thing after my header install. The hoses you took off going to the manifold run down to the A.I.R pump in the front driver side fender. I recirculates air back into your exhaust system, so unless you pull the fuse or take the pump out it will continue to blow air out of the hoses.

ItsNotStock

iTrader: (24)

Could also be built up vacuum in the crankcase coming out of the crankcase ventilation tube which just so happens to vent into most aftermaket lids...

9000th01ss

iTrader: (10)

Yea so how does it make a hissing sound from the lid with the engine off?

I said it's coming from the AC because it can take over a minute for the pressures to equalize in the system, it will do it over a minute with the engine off. And thats normal.

Muerte_X

iTrader: (1)

It's probably the lid, unless it lasts longer than a couple seconds. At idle, your intake manifold and lid are under a vacuum, when you shut it off, the air rushes in. Mine does it too, at a cold/high idle, you can hear the hissing just from the air going into the lid.

My previous car had one of those cone type K&N filters and it was crazy loud, I guess because the pipe to the intake manifold from the cone was like 3 feet long, lol. Damn fwd cars.

andrew69_04

iTrader: (148)

It is not the AIR pump. the airpump only runs for like 15 seconds at initial startup. It will not come on anymore while driving. if hes hearing this when turning the car off, either he has a vaccum leak somewhere, or its A/C related.

RevGTO

iTrader: (12)

It doesn't like you.