I think the ticking and overheating could possibly be two different issues, but not really sure. The header exhaust leak definietely makes a very audible ticking noise. About the overheating, is there lots of fluid in your rad? Have you changed your thermostat lately? Any noticeable leaks anywhere, fluids on the driveway or in the garage? Have you flushed your rad lately? Do you have an electric or clutch fan? Is your fan working? Do you over heat every time, or is it just sometimes, like if you start up your car and just let it sit, will it maintain a proper temp, or does the temp eventually just skyrocket causing it to overheat right away? I wonder if your thermostat is stuck closed?