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Old 11-15-2012, 11:55 PM   #2
Sweetness
E46 is strong with this one
 
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Join Date: Jul 2011
Location: Pittsburgh
Posts: 2,238
My Ride: '01 325i
This could be a crack on the exhaust pipes that is causing this resonating sound. All BMW's (e46's at least) have this sound, very lightly, like a thumping, and is normal. Actual knocking, as in hoarse metallic sounds is probably the lifters in the engine.
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