Join Date: May 2006
Location: Pittsburgh, Pennsylvania
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From what it sounds like, it could be your secondary air pump. What this does is during cold start ups, it pumps more air into the manifold, resulting in lower startup emissions. It should last from start-up for approximately 2 minutes. If you look in the engine bay, it is in the upper left hand corner, it's black and made of a hard plastic of some sort. It appears somewhat of a turbine and has a hose that runs straight towards the front end of the car. Inside is a small filter similar to that of a shopvac. When it collects moisture over time, the filter begins to decay and rot away resulting in a grinding or terrible sounding noise that no BMW should ever make...generally if this occurs and is the problem, the check engine light will come on and if you read the codes, it will list one or two, both having to deal with emissions...check it out and let me know if this what the problem is...