what is that?
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Junior Member
Joined: Dec 2016
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2012 c250
what is that?
Hey guys, I have a 2009 c300..... at times when I start my car I get this loud sound that almost sounds like a scream. i goes away after a bit, but Id like to know what it is.
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Joined: Aug 2013
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2012 C300 4MATIC Sport
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Joined: Dec 2016
Posts: 6
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2009 C300 Sport
Is it only when the engine is very cold?
On very cold start? Like the first in the morning, or after several hours parked...
Sounds like the secondary air pump, I had to replace about 85,000. miles, started getting noisy (high pitch whine).
Tell tell is that sound does not match engine speed...
If you start engine with the hood open it will be very obvious if its the belt or the air pump.
Last edited by gusm325; Jan 18, 2021 at 07:53 AM.
