I have replaced my brother in law's water pump 3 times in his 03. So counting the factory one, his truck is on it's fourth in 135K. That is ridiculous. Yes it is the easiest vehicle i've done one on, but still. That factory one lasted the longest, the next two aftermarkets were terrible. So we spent the $200 (with my uncle's discount) for a factory one again. MAKE SURE YOU POP THE THERMOSTAT OUT AND FILL THE HEAD WITH COOLANT. Learned it the hard way on my first one. The belt tensioner is fine. Am I the only one with this problem? Does not look like they redesigned the pump, nor issued a recall.

 

Just remove the heater core hose from where it goes into the top of the cylinder head before you fill the radiator back up and that will bleed the block.

 

I went to NAPA yesterday to buy a rebuilt waterpump and they sold me a brand new one for less than the rebuild. This is a new pump- no core charge either. I think it is made by Gates. I put it in and it fit perfectly. I'll let you know how it works after I get my petcock to stop leaking.
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04.5 red quadcab 4x4 6spd. manual trans.

 

The aftermarket ones fit great, but they only lasted a year or two. The bearing fails, and the pulley wobbles around with the impeller hitting the block.
I know Gates makes good belts/hoses, I didn't know they made pumps. Hopefully they are better than the ones I bought.