When I accelerate above 2000 RPM, a rattling noise (almost like when a kettle is sitting atop the stove and the water is boiling) comes from under the hood. The sound does not get louder as I accelerate above 2000 RPM (i.e. the sound is constant as long as the engine is above 2000 RPM). I took it to the mechanic, he said that the serpentine belt assembly needed tightening but that did nothing to eliminate the sound. I’m concerned it might be my timing chain. As soon as the engine decelerates below 2000 RPM (say when I put the car in neutral) the noise disappears. It is a 1994 Saturn SL2, manual transmission.
Any thoughts would be greatly appreciated!