I have a 2002 f150 with 4.2L, it recently had what I thought was a bad alternator bearing, is was squeaking a little, I bought a replacement and while installing it, and the belt was off, I started the engine and still heard the squeaking and tapping noise. It sounds like it is coming from the front top part of engine but can't figure out where. The noise also sounds like a lifter does when it is going bad, but read somewhere this engine does not have lifters. Would appreciate any suggestions.