posted 05-07-2002 11:01 AM
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I isolated the noise to this secondary Air Pump (11 72 1 744 490). The noise is like an electric motor having trouble. It only makes the noise during warm-up. It has some clips on the side like it can be opened. While it makes the noise the engine seems to run OK. Before I buy a new one at $180, or open it try to open it, does anyone know if it can be repaired, or maybe there is something lodged in it somewhere.

i had this problem with my 328i 97 also it only ocurred when cold (when the pump is needed) what happened is that the one way valve inside it became a two way valve and sucked in water thus damaging the the pump. fortunately it happened to mine while under warranty

I have a 96 328i also, and I was told that the air pump noise is normal. It is basically a vacumm for the fuel line or something. the noise is normal to come up on startup.

Actually, It's an emissions reduction piece. It blows (supposed to blow) air into the exhaust to reduce hydrocarbons at startup. Mine also filled with water so I guess the valce inside mine is shot too?