Well after pouring through the posts here. Great info by the way. I bought a new cap, thermo and a flush kit. Two hours later and smelling like Dex I still had no heat. Out of pure frustration I removed the intake and return lines to the heater core from the block and used high pressure water to force the flow through the heater core. I ended up using a water baloon filler to get the required pressure.
A few minutes of this and presto. Heat. Prais Jesus sweet wonderful heat. Now it gets so hot on high that you cant stay in the cab for more than a few minutes.
Bravo Zulu to all who contributed to the knowledge base.
It was 11 degrees out this morning. I let the truck run and warm up for 5 min before I drop my son off at school 1 mile away. I have to turn the blower off it gets that warm. Gotta love it! Now the full size company Chevy van is another story.
[size=75][b][color=blue]2003 Blue Crewcab[/b][/color][/size]
Out of pure frustration I removed the intake and return lines to the heater core from the block and used high pressure water to force the flow through the heater core. I ended up using a water baloon filler to get the required pressure. 
