I have a few questions....

1) what is this boiling out of heater cores i keep hearing about
2) i only have three levers in my transporter, what is that fourth one 
   for, i don't have it but i want to know...
3) my heat is not that great..it beat no heat at all,but i think it should
   be a bit hottersNO heat at all, but i think it should
   be a bit hotter...

any hints ?