92 Civic losing coolant and overheating
 

I just bought a 92 Civic 1.5L with 193,000 miles. It runs great when
the coolant level is full. However, after driving for about 30-40
miles, it loses enough coolant to cause the engine to overheat. There
is very slight evidence of white smoke exhaust, although it almost
undetectable. When I start it, there is the smell of coolant that
comes through the vents. I've replaced the thermostat, ECT sensor that
goes to the fan, upper and lower radiator hoses, and the radiator is
new. Does this indicate that I have a small crack somewhere in the
cylinder head? I've always thought that a malfunction in the cylinder
head would render an engine almost useless and since the engine is
strong (when not overheating), I assumed the problem was somewhere
else. If it is the cylinder head, which is the best route to take in
purchasing a new head: brand new or remanufactured? Thanks. Paul