1997 BMW Z3 2.8L
Turns out the loud "wubba wubba" submarine noise is merely the sound of the exhaust, and not the sound of the air pump! (Proved this by starting the engine cold, w/the pump totally disconnected). So the air pump had been dead all along. Replacement pump ($244), replacement valve ($114) = $402, but got a 20% discount (Eastside Bavarian) of $80.So what's with the noise if the pump's dead? Turns out that even with the pump disconnected (or dead), the valve to the exhaust manifold will still open, because that valve is a totally a separate device, on the other end of the air hose. The valve doesn't depend on the air pump to activate; rather, it's activated via a vacuum tube from elsewhere. And the reason the exhaust sound is so loud (and is only heard for 60 secs) is because:
The air pump circuit won't activate unless the engine is totally cold. Then it'll run for about 60 secs, and cut off. You only get one shot, even with an ice cold engine (ie, an engine that's sat in a cold garage overnight). Once the engine has ran for 60 secs, it's now considered "warm" enough to no longer need the air pump. After 61 secs, if you turn the engine off, then on - the air pump will not come back on. So if you want to hear it twice, shut off the engine before it's run for 60 secs.
If you know what to listen for, and you stick your ear right above the air pump, then you will be able to hear the air pump's electric motor. It has a high pitched whine (like a vacuum cleaner motor). You'll hear it best after 60 secs, right when it's about to shut off, 'cause the exhaust manifold valve closes (getting rid of the loud "wubba wubba" noise) one second before the air pump motor turns off -- so in that last sec you can distinctly hear the air pump electric motor.
Even w/a working air pump, you feel a slight out pressure of air at the snorkle (I'd expected to feel suction, since this is the input for the air pump). WTF?
After I'd installed the new air pump, it took 4 days of normal driving before the "check engine" light turned itself off.
I recently puchased a 1997 2.8L Z3. I've noticed my Check Engine sign came on, and the BMW dealerships charge CAN $99 just to check what the problem is. For this reason I am wondering if I should purchase an Engine Fault Code Reader which can reset the Check Engine sign also..... for US $150.
