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loud humming noise

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Old 02-10-2005, 06:08 AM
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Default loud humming noise
driving a 99 2.8 A6 with about 83k on the clock. recently there is a loud humming noise coming from the engine compartment. the best i can tell it is on the left side (standing in front of car). if will hum for about 45 seconds to 1.5 minutes and then stop?

anybody have any ideas as to what it might be?

thanks in advance.
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Old 02-10-2005, 06:29 AM
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Most likely the secondary air pump. Does it mostly happen on initial start up? Very common.
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Old 02-10-2005, 06:50 AM
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Default Hum when? When you start it, or when you shut it off?
On startup, it's the secondary air pump. on shutoff, it's the coolant afterrun pump. Both devices are in the passenger side of the nose.
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Old 02-10-2005, 06:51 AM
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Could be the 800 horsepower acting up.
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Old 02-10-2005, 07:02 AM
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Re: loud humming noise - its is on start up
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Old 02-10-2005, 02:17 PM
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Auxillary air fan used for emissions upon start-up. Normal.
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