Water Pump Thermostat Outlet Size?

[tony17112acst]

I have searched these and other forums and cannot find an answer; I'm a bit of a novice:

I am going to replace my 2004 Rainier's 5.3L water pump. When I called the local parts store for a price they asked me if I need the pump with the 2.05" or 1.88" diameter thermostat outlet. Huh? Then I searched online for the pump and found the same two choices!

#1) How do I know which one to order?

#2.) Do I **NEED** to order the bolt kit I see advertised with the pump, or is it optional?

Thanks in advance! -Tony

 

[tony17112acst]

No help?

Well, I decided to tear the water pump off today. I measured the thermostat opening on mine and it's 1.88", not the 2.05."

I found a parts store that had both sizes but when I went to pick up the 1.88, we found the opening to be 2.05." At the parts store, we checked and double checked and it's supposed to be 1.88. They have nothing else in stock, so I walked out with it knowing I could return it.

Now, it looks like my 1.88 will actually fit the 2.05" opening. The parts store had nothing else in stock. Should I try it or will it leak. The difference in the opening is really small (2.05 - 1.88 = .17") ...about an eighth of an inch and since it's a diameter, it's another half of that.

I can't believe no one here has come up with this 1.88 vs. 2.05 thermostat diameter opening with all of the water pumps being changed out. Maybe it was only for 2004?