1997 BMW 328IC loud grinding whining noise from engine

[mlanthorn]

We have 1997 BMW 328IC with about 70,000 miles on it. When you start it there is a high [B]pitched noise and it i[B]s coming from an engine part that [B]is in the left side of the engine up by the windshield. when you put your ear down to it, you can tell that the noise is coming from it. what is that component of the engine so we can replace it.

[Manolito]

This stumped me for a while until I realized that you may mean the 'left side of the engine' when viewed from the front of the car. Is that the case?

If so, does that part look like a vacuum cleaner fan in a plastic housing?

That would be the secondary air fan that runs for a couple of minutes after a cold start.

What usually kills these is that the check valve on top of the front of your exhaust manifold starts leaking, and it blows wet exhaust back through the secondary air fan. Spinning backward all day and being full of condensed water trashes the fan motor bushings pretty quickly.

Good news - it can be rebuilt. Bad news - you can't rebuild it unless you fabricate a special puller to carefully remove the fan from the motor shaft.

Good news - there is a shop that advertises on EBay that will rebuild these fans in Volvos for about $120. The e36 BMW uses about the same fan and they will rebuild it. A new fan is over $300. Bad news - assuming that your check valve has failed, it cannot be rebuilt, and it costs another $120.

If you pull the hose off the check valve when the car is warm (fan not running) and you hear exhaust leaking through it, the check valve has failed. Or, if you pull off the fan and you pour water out of it, the check valve has failed. You can drive your car without that secondary fan while it is being rebuilt, but the check engine light will come on.

Be careful of the little soft rubber mounts that hold the secondary air fan. They may tear in two when you loosen the nuts unless you carefully hold them with a wrench. There are flats at the ends of the rubber mounts where you can hold them with an open-ended wrench.

While repairing this, unbolt the computer connector and clean the ground connection on the fender beneath that computer connector. That ground tends to corrode, and cleaning it every decade or so will prevent electrical gremlins down the road.