Hey guys, I'm fixing to put a new waterpump on my truck since the stocker seems to be leaking.

Looking online it seems there are pumps with a 1.88" thermostat outlet and some with a 2.05" outlet.

My truck is a 1999 silverado ext cab lt 2wd with the 5.3L.

The obvious answer is that, I should measure the outlet myself, but I don't have the ability to pull it and then go buy the part. If anyone knows which one I need, I'd greatly appreicate it.

 

Any help with this? I'm debating on buying both and returning the one that doesn't fit, but this would save that trouble.

 

i'm looking for the same answer. i just recently replaced my thermostat and at first got the one piece design which would not fit in my housing (too big). the two piece fit in there which was great because it was cheaper. i'm reading that 04-up Gm switched to a two piece thermostat/housing. i want to confirm size before i order a new pump although from my experience i'm guessing the two piece design is the smaller 1.88" outlet. i measured the size of the one piece thermostat to confirm it was larger than my original and it was right at 2".