BMW E46 Fanatics Forum banner

1 - 19 of 19 Posts

·
OG e46fanatics lurker!
Joined
·
2,067 Posts
Discussion Starter #1
i get this very brief suction noise from under the hood everytime i shut off the engine. its very brief, only heard for about a second. it sounds like a fast gust of air being sucked into somewhere but i cant figure it out. anyone else notice this?
 

·
OG e46fanatics lurker!
Joined
·
2,067 Posts
Discussion Starter #3

·
OG e46fanatics lurker!
Joined
·
2,067 Posts
Discussion Starter #6
have either of you asked the dealership if this is normal yet?
 

·
OG e46fanatics lurker!
Joined
·
2,067 Posts
Discussion Starter #8

·
OG e46fanatics lurker!
Joined
·
2,067 Posts
Discussion Starter #10
MiamiBimmer said:
Its the air conditioning exterior vents closing...same sound happens when you turn off your A/C when the car is on/running/idle/etc.
that might be it...but sometimes when i have the accessories on, i hear the vents close. but that takes like 6+ seconds and its a slow deep noise... so i could be hearing something else..not sure :dunno:
 

·
Likes Supermodels
Joined
·
2,776 Posts
it's normal, i had the same scenario with the e36(rip)
 

·
Registered
Joined
·
1,500 Posts
Completely normal; the gasp of air after shutoff is just pressure releasing from the system.

There was a post by Sev1980 from 2008 who describes it in a bit more detail:
i took apart my entire intake tract and stuck a mirror inside and spent a good 10 minutes starting and stopping my car. I finally found what causes it. As the Throttle body gets old, the motor gets a bit of play in it. When you shut the car off, there's a bit of vaccuum in the manifold that pulls the TB shut. As this vacuum pressure starts to go, it lets go of the worn TB and all of the vacuum rushes out. Hence the SWOOSH...
Edit: for more info on the "gasp" of air after shutoff, see this thread: http://forum.e46fanatics.com/showthread.php?t=1067604 and the 4 minute mark in the video below to see things in action.

https://www.youtube.com/watch?v=FYBaJAF0o14
 

·
Premium Member
Joined
·
28,970 Posts
Wow, 10 year old thread bumped back to life, may be a new record?

Normal noise, this is a good thing, means the crankcase is at least somewhat tight. Also you should head the DISA open up as well if you know what to listen for or you have the hood open.
 

·
Registered
Joined
·
10,207 Posts
i get this very brief suction noise from under the hood everytime i shut off the engine. its very brief, only heard for about a second. it sounds like a fast gust of air being sucked into somewhere but i cant figure it out. anyone else notice this?
It's nothing to worry about.

An engine is nothing more than an air pump. It sucks air in one side, and blows air out the other. It does stuff in the middle, but that stuff is not part of this. You are hearing the last gasp of sucking as a piston is going down on the intake stroke. It is absolutely nothing to worry about.
 

·
Registered
Joined
·
37 Posts
Completely normal; the gasp of air after shutoff is just pressure releasing from the system.

There was a post by Sev1980 from 2008 who describes it in a bit more detail:
Perfect, that's the answer i was looking for.. thank you.:thumbup:
Wow, 10 year old thread bumped back to life, may be a new record?
Lol, well you know i like to hit that search button that most people forget to use. :read:
 
1 - 19 of 19 Posts
Top