It could definately be a water pump... My g/fs Civic LX engine had a similar 'knocking' sound... I was hoping it wasnt a rod knocking... Turns out it was the water pump, it completely came off the 'axis' or bearing or whatever it is it sits on... The bad part was, she drive it home overheated when it finally blew... :doh: Didnt hurt the engine tho atleast not right then and there... I put a new belt and stuff on, and it ran fine... Unfortunately, the engine did die about 6 months later... Whether or not it was related, I dont know for sure...