Whinning noise at cold start up - smog pump?
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Joined: Apr 2011
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E55 AMG, Hummer H2
Whinning noise at cold start up - smog pump?
I'm referring to the motor pumps that supposedly warm up the cats during cold start-ups.
Recently, I'm getting a somewhat loud whinning sound as soon as you start the car and then the noise lessens and disappears after 30 secs or so.
Is this the smog pump starting to go bad? I'm just wondering if it's okay to wait until it dies (and get a CEL) before I replace it, since the noise goes away anyway.
It doesn't have any impact on drivability and performance right?
Has anybody here replaced theirs?
Recently, I'm getting a somewhat loud whinning sound as soon as you start the car and then the noise lessens and disappears after 30 secs or so.
Is this the smog pump starting to go bad? I'm just wondering if it's okay to wait until it dies (and get a CEL) before I replace it, since the noise goes away anyway.
It doesn't have any impact on drivability and performance right?
Has anybody here replaced theirs?
Super Member
Joined: Jun 2008
Posts: 855
Likes: 2
2010 C63
There are 2 different noises on cold start. the smog pump is a high pitched whistle that's a constant pitch and will go away completely after a few seconds. It will also come on from time to time.
The 2nd is a buzzy whine that many people think comes from the oil pump area. this noise will change pitch with RPM. On mY C55, the noise is loud when cold and gets quieter when warm but never really goes away completely. The sound is still there when I remove the serpentine belt which means it's not coming from any pullies or accessories.
The 2nd is a buzzy whine that many people think comes from the oil pump area. this noise will change pitch with RPM. On mY C55, the noise is loud when cold and gets quieter when warm but never really goes away completely. The sound is still there when I remove the serpentine belt which means it's not coming from any pullies or accessories.
MBWorld Fanatic!
Joined: Jun 2009
Posts: 3,040
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From: Atlanta Metro
Current: C217 V12TT AMG Previously: C55 AMG, SL65 AMG
The smog pump is an annoying wahhhhh that lasts for about a minute on startup. It is normal, I'm surprised you never noticed it before.
The high pitched whine that lasts a few seconds I have yet to fully figure out, but I assume it's the alternator regulator.
The high pitched whine that lasts a few seconds I have yet to fully figure out, but I assume it's the alternator regulator.
