its a 1997 toyota celica and whenever the car is hot (usually later at night) the car starts to make this sound as if 2 small this pieces of metal were rattling and hitting each other. i have opened up the hood and had someone step on the gas while im trying to see if theres anything rattling, but to me it seems like it may be coming from either inside the engine or maybe under (and thats why i couldnt see anything from the top). i hope that it isnt some little bearing or something inside the cylinder head, but i just cant pinpoint that darn thing. and i usually hear this later at night (maybe because that car has been hot all day) and usually when im at 2,000 - 3,000 rpm. the car has 128,xxx original miles. any suggestions will be really helpful. thanks!!!!