Knocking sound

I just had my water pump replaced and when I started my car back up, it was making a knocking sound. I looked at the mechanic and he said that pressure needed to build back up and it should go away in a couple of days. It's been a couple of days now and the sound is still going on. Any ideas? I'm taking it back tomorrow, but I want to go with some knowledge so I can agree/disagree with him. Thanks.

Tell your mechanic that its BS!!! A water pump replacemnet should not make the engine knock!!!

You didn't say what engine you had so its hard to guess what the problem is!!

It's a 2.4L DOHC in a 1998 Pontiac sunfire gt. It sounds like it's near the pulley side of the engine, the alternator, the motor oil refill cap.

The mechanics at Pep Boys are completely retarded. They were correct in telling me that the problem lied in the timing chain tensioner, but there is something on it that needs to be released so the pressure can build up so it pushes against one of the guards for the timing chain. After they replaced my water pump, they forgot to release this again, therefore, causing the knocking sound that I heard. It took a second opinion from the sound and a diagram for me to show them what was wrong. Hope this helps if you ever get a knocking sound after getting your water pump replaced.