About 4 weeks ago, I heard a noise that my mechanical friend told me was a bearing going out. It was louder at higher RPMs. It went away after 2 days. Now it is back and has been making the noise for about a week. My mechanical friend used a "stethoscope" type tube to see where the noise was loudest and eliminated the alternator, A/C compressor and power steering. He said the noise was either the water pump or something related to the timing chain. He could not be sure which was the source since the noise was loud near these 2 items. I have already put a lot of money into this truck last year and am quite unhappy about this. I would like some input as to what I might do to determine the source of the problem. I don't know how serious this is and whether I should just take it to the dealer. Thanks for any help.