My 1999 4.2L regular cab makes a "tick,tick,tick,....etc" sound at idle. Is it just a belt, and will it hurt anything if left unfixed? Also my rear brakes screech really loud when coming to a slow stop. My brakes were replaced just a couple of weeks ago so any ideas would be nice. Any educated guesses would be greatly appreciated. thanks

 

Could be a bad lifter causing the tick, it's hard to say.
Were the drums/discs turned or replaced when the brakes were done?