1986 Fiero V-6 Heating Problem - 70,000 miles all of sudden temp goes all the way to top no stop.... changed thermo and burped the system, filled it as required. In about 10 minutes temp gage goes to top.... prior owner swears it never overheated - I suspect radiator stoppage or water pump problem.... Question is can this delay in heating also be a head gasket or cracked block, head expantion once car gets warm? Had a couple of Fieros and never had this kind of problem. Live in Las Vegas so plenty hot....