2003 Subaru Legacy Cooling System issues

Engine Cooling problem
2003 Subaru Legacy All Wheel Drive Automatic 85000 miles

I drive a 2003 Subaru. I have had a couple of times when my coolant was low. It has also been smelling hot. A couple of weeks ago the temp gage when really hot and the engine started steaming. A slight leak was also noticed. I had the water pump, thermostat, (and timing belt) replaced. When I got it back the temp gage started to go up again but no steam or leaks. The mechanic replaced a faulty thermostat and the problem seemed fixed for a couple of days. Then I drove 100 miles or so and the next day it started steaming and leaking again. The mechanic then replaced some gasket that he said he missed. It is now overheating again but when I turn on the heat and fan on high the temp gage goes down. If I turn it off it goes back up. It is also smelling and slightly steaming again. Any ideas on what this is? Does this mechanic seem to know what he is doing