I changed the timing belt and water pump and when I started the car up. At first, it sounded normal for about a minute then, the engine idle very rough. The revs bounces up and down from 1000 to 3500 back and forth. It sounds like a vacumm leak but all hose seem to be in place. After about 10 minutes of idling, the car starts to over heat. What can this be? Could it be the thermostat? Thanks for any help.

 

since you changed the water pump, I'd guess the overheating is related to that somehow. If the pump wasn't pumping, you'd overheat pretty quickly. Or you could have an air bubble in the coolant system. bleed it.

a poor running motor after a timing belt change is a sure sign you're off by a tooth