[Fbo_n54sfv]

When I shut off the car I hear air hissing kinda sounds like steaming. Anyone experienced this and know what it is ??

https://youtube.com/shorts/ekAgQQaL_no?feature=share

[Bimmer_Bro]

Originally Posted by Fbo_n54sfv

When I shut off the car I hear air hissing kinda sounds like steaming. Anyone experienced this and know what it is ??

https://youtube.com/shorts/ekAgQQaL_no?feature=share

After you shut the car off and the hissing stops. Unplug one of the vacuum hoses from the black air canister. (A healthy vacuum system should stay pressurized for a while after. )
When you pull a hose off, do you hear hissing out of the black canister ?

Have you ever done your vacuum lines and boost solenoids?

[Fbo_n54sfv]

Originally Posted by Bimmer_Bro

After you shut the car off and the hissing stops. Unplug one of the vacuum hoses from the black air canister. (A healthy vacuum system should stay pressurized for a while after. )
When you pull a hose off, do you hear hissing out of the black canister ?

Have you ever done your vacuum lines and boost solenoids?

Yes I have upgraded vacuum lines. I also don't have boost problems running 18psi. I do hear the vacuum system loose pressure once I disconnect the line from the canister when car is off so I know the leak isn't the vacuum lines.

[TheMidnightNarwhal]

I have similar noise and I just thought it was normal. I don't really have any performance issues.

[Fbo_n54sfv]

Originally Posted by TheMidnightNarwhal

I have similar noise and I just thought it was normal. I don't really have any performance issues.

I don't notice performance issues either. Please check my other post, that's what I'm tryna figure out too.

[Fbo_n54sfv]

Originally Posted by TerminatorStout

I am willing to be it is water being circulated into your turbo's, (that first initial hiss sound is the coolant turning to steam just like you thought) which I believe is the reason the water pump runs after the car shuts off.

You should really let your car idle in the driveway for 2 minutes before shutting it off.

Some people will tell you to drive "less spirited" for a couple minutes or miles before you get to your house, but the N54 is designed use the turbo's very early in the RPM range so unless you seriously drive it like the stupid prius driver in front of you trying to keep the "fuel meter in the green", your turbo's will still be hot.

Interesting, I did think it had something to do with the water pump still running for a few seconds after the car is shut off. I do have BSD fault codes including water pump/alternator/ibs missing. Is this something I should worry about?

[Fbo_n54sfv]

Originally Posted by TerminatorStout

When researching these noises I have also heard that evap pump, blower and other things happen as well after the car shutoff so could be related. I suppose it could be part of an emissions / charcoal canister purge? Are you running AC currently in humid conditions?

You should post the codes up here so people can read and chime in, I am just learning the platform, mechanic for a long time, but these are a whole new animal.

I never heard of those things or found anything similar to this. I never use AC. Yea here the codes. Definitely a different animal.

[Fbo_n54sfv]

Originally Posted by TerminatorStout

After seeing the codes my immediate reaction (without much thought) is that your water pump is either failing, or your coolant is low or both. The hissing sounds you hear is probably water going into the turbo's as I mentioned before but probably because you have air bubbles in the system from either the two things - water pump, low coolant.

The other codes (without thinking much) you have aftermarket accessories plugged in somewhere and your ibs is either unplugged, was unplugged momentarily while on, or your alternator is starter to fail - any electrical or battery issues?

Yes actually my coolant is low, I will fill it up and bleed it and see if the noise goes away. BSD fault codes might be due to the alternator not being oem (doesn’t look like it) and is bringing down the whole commication line. But it might be another part.. haven’t figured which one is.

[Serf27]

Sounds like coolant flowing through the system and pushing air around.
Never heard such noise on my n54.

[Fbo_n54sfv]

Update:

I filled the coolant and bleed the system and it’s still making the same hissing noise.

[Serf27]

Is the A/C on when you shut it off?

[Fbo_n54sfv]

Yes ac never on

[Serf27]

Yes, how did you bleed the system?
Common way or bmw way?
I ask about the Freon because I have actually heard a similar noise (air moving around) on my e93. When the Freon was low and the car is shut off, it would make a noise like yours in the video.

[Fbo_n54sfv]

I only added coolant then activated the bleed procedure once which was about 12 minutes. Should I run it a few more times ?

No coolant leaking from turbo lines.. it sounds more like it’s coming from top of the valve cover on bank 2. ( New vc, vcg, pcv hose, upgrade pcv)