water

I have an 04' Alero, 2.2 ecotec.. Two weeks ago my muffler sounded like i had water gurgling in it. Now the muffler sounds like it has holes, but there are no holes. Any idea to what this could be? No check engine light, I was thinking maybe a clogged cat but I'm guessing no. It doesn't smell or...

well tomorrow I'm replacing the water pump on my 2000 oldsmobile intrigue 3.5. Does anyone know the proper procedures and have some advice for me? Thanks