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Old 11-15-2012, 11:55 PM   #2
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Join Date: Jul 2011
Location: Pittsburgh
Posts: 2,272
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.
2001 325i ZCW, ZPP
Titansilber Metallic, Black Interior
The 160,000 mile, clean daily driver
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