hoping this is a easy one, 2004 trailblazer, 4.2 six. water pump so bad that when the engine revs up the fan vibrates enough to hit the fan shroud, not sure why it hasnt leaked coolant badly. from the looks of the replacement part at autozones website, looks like once the fan & pulley is off, thes 4 or 5 bolts holding the pump to the block. are the threads on the center stud for the fan clutch r.h or lh thread? think getting that loose might be the worst part.

 

The threads on the stub of the water pump are standard right hand threads (lefty loosey, righty tighty). An 1-7/16" wrench & a hammer will break the clutch loose fairly easily (or should). If it proves resistant, get a breaker bar onto the belt tensioner & have an assistant tighten the belt using the breaker bar while you smack the wrench with the hammer to shock it loose. I have also used a strap wrench on the water pump pulley before to hold it steady for the really persistent clutches.

 

got it done, loosening the fan clutch from the pump was the worst part, my homemade flat-iron spanner wrench bent up on me and i ended up running a chain from one of the pulley bolts (and had to get a longer bolt) to the engine lift eye. did the brakes on this truck 2 days ago, that was very quick & easy, it did snowball into finding 2 other issues, the very noisy, loose water pump and both tie-rod ends are bad. guess thats my next thing once i read up on it, shouldnt be too bad. its a co-workers truck, not mine or i would probly have it done already.