Well I pinpointed my diesel-like cold startup sound to the air pump, just above the alternator. I disconnected the relay this morning and no noise; plugged it back in and sound returned.

The noise does go away after about a minute of warmup time, but it's annoying as hell. My question is, what's it's purpose? Is it emissions-related, because I notice some of the older 300E's don't have this. Mine's a '91.

I'm considering just unplugging the sucker if it is not an integral part of the engine and is simply an emissions reducer. I know that sounds environmentally irresponsible but it's better than spending $450 for a new pump.

Any insight would be appreciated...

TIA

Iodyn