First, try putting the trans in neutral when the sound is very loud, just to be sure it is not the wheels/axles or the fan, which will keep running even though the engine drops to an idle. If the sound diminishes sharply, then it is something related to the engine which could be the engine, the transmission, the alternator, the power steering pump, of the AC compressor if the AC was running, as all those are powered by the engine. If it is the engine, then I would stop, then rev the engine while the car is at rest and in neutral and bring along a knowledgeable person to open the hood and listens for the source of the offending sound.
Ideally you will pinpoint the source that way.
Tuesday, October 28th, 2014 AT 11:57 PM