How do you change a water pump? - 2001 Chevrolet Blazer

1)Drain the coolant:
2)Remove the shroud: 7-10 mm bolts
3)Remove the fan and clutch: There is no need to separate the fan from the clutch. The whole thing threads on to the end of the water pump. I don't know the size, because rather than break out all my wrenches, I just grabbed an 18 inch crescent wrench. Place the wrench on the nut and tap loose with a hammer. the tapping will break it loose. You have to tap it, if you just try to loosen it, the belt won't hold it and the whole thing will turn. After it breaks loose just spin it off.
4)Break loose the bolts holding the pulley on: 4- 13 mm or 1/2" bolts Just break them loose, don't remove them
5) Remove the serpentine belt
6) Remove the pulley: Finish removing the bolts holding the pulley and remove the pulley
7) Disconnect the hoses
8) Remove the old pump: 4-14 mm or 9/16" bolts
9) Clean the surface: Remove all traces of the old gasket.
10) Install new pump: Apply a bead of blue permatex around the holes on both sides of the gaskets, put them on the pump and insert the bolts through the holes to hold the gaskets in place. Carefully lower the pump in to position. Thread the bolts into the block and snug them. Then remove the bolts one at a time, add the permatex to the threads, and then reinsert. (only do one at a time so that the pump doesn't shift and disturb the mating surfaces) Then tighten all the bolts.
11) Reinstall everything in reverse.
There will be a lot of air trapped in the system, so after you fill it, get the engine to operating temperature, shut it off, let it cool, then add more. The air trapped in the system can cause your engine to over heat if left unattended. I suggest filling the system with water only and run it like that for a day or two just to make sure there are no leaks. That way you don't waste your antifreeze if you have to do further repairs. 
Good luck and hope this helps.