I need to changed water pump, thermostat and flushed old coolant?

Disconnect the negative battery cable.
Drain and recycle the engine coolant.
Remove the air cleaner intake tube (if necessary).
Remove the upper radiator hose.
Remove the fan shrouds.
Remove the engine fan.

WARNING
Do not place the viscous fan drive assembly in the horizontal position. If placed horizontally, the silicone fluid in the viscous drive could drain into its bearing assembly and contaminate the bearing lubricant.

Remove the drive belt(s).
If the vehicle has V-belts:
Remove the alternator.
Remove the bracket that supports the alternator, compressor or idler pulley (without A/C). The compressor will be supported by a rear mounting bracket.
Remove the air pump.
Remove the power steering pump front mounting bracket (if equipped). It is not necessary to remove the hoses. Support the power steering pump with mechanic's wire or equivalent.

If the vehicle has a serpentine belt:
Remove the water pump pulley bolts.

Disconnect the lower radiator hose from the water pump.
Label and disconnect the heater and bypass hoses from the water pump. On later models, to ease installation, remove the pump before you remove the bypass hose.

On some later models, it may be necessary to remove the heater hose tube; this is done by removing the bracket and twisting the tube to release. Discard the old O-ring and replace with a new one for reassembly.

Remove the water pump retaining bolts, noting their location.
To install:

Clean the gasket surfaces thoroughly.
Install a new gasket and position the water pump on the engine block. If necessary, guide the bypass hose on at this time.
Install the bolts, in their original locations, and tighten in a crisscross pattern to 30 ft. Lbs. (40 Nm).
Install the heater hoses, and bypass tube, if necessary. Tighten the clamp on the heater hose placed on the pump before the bolts are tightened.

On the models where the tube had to be removed, install the tube into the water pump with a new O-ring, and tighten the bracket.

Install the lower radiator hose.
On models with V-belts:
Install the power steering pump and bracket.
Install the air pump.
Install the bracket to the alternator and the air conditioning compressor (if equipped).
Install the alternator.

On models with a serpentine belt:
Install the water pump pulley bolts, and tighten to 20 ft. Lbs. (27 Nm).

Install the drive belt(s).
Install the viscous fan assembly.
Install the fan shrouds.
Install the upper radiator hose.
If necessary, install the air cleaner intake tube.
Connect the negative battery cable.
Fill and bleed the cooling system.
Check the cooling system for leaks.

The cause could be a misajusted tension of the belt.
A slipping belt overheats and becomes glazed and eventually fails to drive the water pump. This can cause overheating, causing pouley to wear out
A belt that is too tight can place a severe strain on the water pump bearings, causing them to fail.

Use a torque wrench ( at proper specification)
use a belt tensionner gage to mesure the tension.

Good luck.

When you say "new" do you mean aftermarket or OEM. Doesnt make much sense considering that has an automatic belt tensioner.I would probably go to the dealer(as much as that hurts) and get a new OEM pump

We had problems with particular brands of pumps. The most reliable that I have found is Napa's new durapro pumps. Very rare is there a problem.