Is it a knocking, ticking, or chattering noise? You can pull the valve covers off and inspect the top of the timing chain. If the chain is stretch to much it is possible for the engine to jump a tooth and jump timing. Does the engine start with no problems or does it turn slow when you attempt to start it?

In addition, you posted early that you have a coolant leak, is there coolant found on the oil stick? Please give us more information on the noise you hear once the engine is running.