Vacuum Sound at Start Up

07SMLT

Original poster
Member
Aug 30, 2012
4
Ok, I did a search, but can't seem to find any references to my issue.

I have a '07 LT. It makes a weird sound on start up when it's cold. The only way I can describe it is it sounds like a muffled shop vac. Starts instantly, then fades out. Last for anywhere from 10-40 seconds. Any ideas?
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Totally normal and expected. It's the SAIS (Secondary Air Injection System) turbine air pump. It injects air into the exhaust manifold to hasten the engine control's entry into their low-emission closed loop mode.

Sometimes they get filled up with condensed water and freeze or break or make extra noise. Keep watch for this.

ADDED: They sit on the frame rail underneath the truck below the driver's seat.
 

07SMLT

Original poster
Member
Aug 30, 2012
4
Wow, that was fast! Roadie, you are the man. Thanks for your help here and at offroadtb.com.
 

silverunicorn

Member
Dec 4, 2011
327
I bet it's just like this :smile:

[video=youtube;pOdidnHcPhU]http://www.youtube.com/watch?v=pOdidnHcPhU[/video]

And, as always, Roadie is correct.

Chris
 

07SMLT

Original poster
Member
Aug 30, 2012
4
That's it! Sounds like a "muffled shop vac", right?

Yes, I'm new, but it's easy to tell that Roadie is like a TB/Envoy wizard or something.
 

silverunicorn

Member
Dec 4, 2011
327
07SMLT said:
That's it! Sounds like a "muffled shop vac", right?

Yes, I'm new, but it's easy to tell that Roadie is like a TB/Envoy wizard or something.

Indeed!

I like to think of The Roadie as the Trailblazer "Rainman"

:smile:

Chris
 

07SMLT

Original poster
Member
Aug 30, 2012
4
Bwahahah!! :rotfl:

Only on Sunday, o-o-only in the driveway, d-d-definitely boxer shorts...Kmart sucks!
 

vipergg

Member
Dec 7, 2011
191
scottp8113 said:
Just wanting to confirm that I have a similar noise and not start a new thread. Only mine makes code 0411 pop when it dies down...

https://skydrive.live.com/redir?resid=F279CCF38ED96132!617&authkey=!AMOTzZunn0xxMtI

That means there is some sort of issue with the secondary air injection setup. Not seeing enough air from the pump or the valve is stuck or not functioning correctly. Most times it appears to be an issue with the valve . I got this a little while ago and then it just cleared itself and haven't seen it in like 3 weeks . Here is a whole TSB for troubleshooting this from a dealer perspective. http://www.2carpros.com/questions/chevrolet-trailblazer-2006-chevy-trailblazer-p0411-code
 

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