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      09-19-2013, 01:10 PM   #1
polar
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Engine knock at cold start

My car has just started to make these weird knocking sounds. What is it trying to tell me? Check the video at 0:19 and 0:27.
It's only hearable at cold starts, and just when the revs drop from about 1200 to 900. It sounds like it's coming from somewhere below... There is a few knocks and after that it's "quiet". There is no other strange noises, vibrations or warning lights.

I've had the car for six years and it has 34000 miles on the clock. Oil and filter is changed every 3-4k miles. Its never been tracked and I have never ever redlined it.

I hope its just something like carbon buildup, but if someone knows, have an idea, hunch or comment about this, feel free to chime in!

Enjoy video (or not):


Last edited by polar; 09-19-2013 at 02:03 PM..
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      09-19-2013, 01:19 PM   #2
Beedub
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sounds rotational . i,e like rythmic with the belt ect ect
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      09-19-2013, 02:15 PM   #3
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You need to get a mechanic's stethoscope and use it to localize the sound. Knowing where it's not coming from can lead you to the source. It may take a number of cold starts, but eventually you will track it down. From the sound quality and short duration could it be the air pump?
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      09-19-2013, 02:39 PM   #4
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Quote:
Originally Posted by Beedub View Post
sounds rotational . i,e like rythmic with the belt ect ect
hmmm... belts etc you say? I youtubd that and it sounds very much like failing water pump bearings on a E46.

Incompatible, I'll utube the air pump...
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