Yesterday, I flushed the cooling system for almost two hours. Lots of orange/brown crud came out. After flushing, the upper hose and the hose that goes from the pipe to the thermostat got replaced too. Still need to replace the lower hose but access was a problem.
Gutted the old thermostat (used it in place of a washer), filled the system with Peak Super Flush and distilled water. Within 10 minutes I was getting heat and there were no leaks. I had to rev the engine to 2500 to get heat at first. I suspect that the missing thermostat must have played a role on that. After that, I flushed the heater core and radiator one more time. Now I am waiting for a new thermostat and I will put it together as you suggested. The lower hose is not leaking but I have a replacement hose and feel obligated to replace it. Do I need a special tool to remove the clam from the water pump?
I decided to go with Prestone yellow extended antifreeze and see how it goes. If it ends up being a head gasket issue (very possible with a neglected 105,000 engine), I will switch to green coolant and use a bottle of Steel Seal. I have had good luck with this sealer in the past although it is very pricey. It can be also used as a preventative measure to fill any small block and gasket imperfections. It will not plug anything either.
Hope the issue is resolved and I can move on to the transmission, brake fluid and PS flush before I can have my teenage son start driving it.
Thanks amc49 and I hope this discussion was useful to other forum members.
Last edited by diexodos; 10-05-2012 at 04:59 PM.