My wifes M3 had a check engine light pop on...codes were for bank 1 something... anyways replacing the airpump. What is the function of this thing other than to reduce emessions on cold start, I looked on the one on her car and it appers to have a filter in it which is all clogged with what looks like oil and smells like fuel. only assuming thats bad. Next question can you just replace the pump filter or is a whole unit deal? Thanks
Usually, the secondary air pump is siezed, which is what causes that CEL code. It is very common. If you do not hear a vacuum cleaner sound from it for about 2 minutes during a dead-cold start up, it is likely seized. To test it you would want to check the fuse and jump out the pump relay. If you still don't hear anything, it is bad. You may also wish to repace the secondary air valve (which bolts a pipe right above the exhaust manifold) as a common diagnosis is that the valve goes bad, leaks exhaust gasses at the pump, which are corrosive, and kills the pump. There is a solenoid that controls the vacuum to the secondary air valve that you should test as well just to be safe, but I have not seen a bad one yet. The pump is not cheap, and you cannot get the CEL to go out without fixing it (sorry) but you should make sure the rest of the system works properly too.
got the new one in today.. wow I must say the filter inside the new one makes me think Something else was up with the one I'm about to replace I think Im going o order that valve to be sure Im in the clear.
A secondary air pump came with my euro motor (among other things). I looked at it and said "I don't need this crap" and tossed it in the trash. Haha. Not having to legally smog a car is pretty sweet.
