We are looking at a nice 2012 Z1 that seems to do everything right except for a strange sound neither the seller nor I, nor even the BMW tech we took it to for inspection could identify.


It show now Check Engine, nor shows any codes as scanned by the independent shop I brought it to for a buyer's inspection.


When the engine is started, prior to eng cranking,there is a buzzing sound that runs about 1 - 1.5 seconds, then stops. Same after the engine is shut down. It sounds like a loud hum, or vibration somewhere in the engine bay, but we can't tell where exactly where it's coming from.


I have a Mercedes Sprinter van that has almost exactly the same symptom, but in that it was easily identified as an auxiliary coolant circulating pump that is used to recirculate coolant from the engine through the heater core when the engine is not running to use the residual engine heat after shutdown to heat the passenger compartment for a while. I simply unplugged the pump's electrical connection until I could get to replacing teh pump on it.


I don't have a CLUE if the X1 has such a pump buried somewhere out of sight (long shot), but the noise is almost too similar both in when it happens, and the sound of the noise to be 100% coincidental.


I could also loosely compare the sound to a noisy fuel pump older BMWs would make when turning the key to position 2 to prime the fuel system prior to start, but noisier.


Anyone know if there IS a recirc pump under the hood or something that might operate at the times mentioned?


Thanks-
Bob