Leo wrote:
When I turn on the hot water faucet in a sink or shower it 'sputters' as if
there is air in the line. I have not done any plumbing work that would have
caused this... what is happening? I can't find any obvious leaks
anywhere???

The water line is pressurized so an leak would not admit air. Maybe
your water heater is set too high and there is boiling happening.