[forest]

i have problems with the heat in my truck. I have changed the following;

Clutch fan
Radiator
turpentine belt
Thermostat
Water pump.

all these parts were required, however....I still don't have very much heat in my truck....a mechanic said I need to check my head gasket and possible change it. I also heard it may be some vacuum hoses that control the heat. Anybody else have this problem? What can I do? Please help.