OK, here is my saga. I just drove from CA to AK (thats Alaska, not Arkansas)- I have a '84 245 w/ 270k. The radiator is from a mid seventies, I've run with it for a year now, because the stupid plastic original cracked and while the Junk yard rad has always run a little hotter than the old one,it never OVERheated, and I figured it was just a little clogged. So I'm doing a thousand miles a day the past few days, keeping up with the truckers on the ALCAN, and I start noticing alot of coolant disappearing- in the middle of the day, air temp around seventy; probably adding a gallon of H2O every two hundred to one hundred miles. Bad. I know. At night, or at 55 mph, temp would be reasonable, but still hot. But no coolant/H2O consumption at night. Expansion tank develops incredible pressures, I could see it swelled up. After slowly bleeding off the pressure, and adding H2O, I'd go on my way for another while... So Now I'm almost home, another two hundred miles. I went to a parts store here in Anchorage and got some radiator flushing solution; HCL (Acid) I believe. And my car ran just fine around town, no over heating at stoplights. I am in a friends driveway, and I proceeded to flush the system with a hose, and then I added the cleaning solution, and started the car, IT NOW BOILS OVER IMMEDIATLY UPON STARTING, almost before getting hot. The engine feels hot, but the tank and Rad are just developing pressure and no heat.
Aha, it's the thermostat you say. Well, before adding the cleaning solution, I took out the six month old thermostat, and checked it, and it's opening just below boiling (on the stove top) so it's good. Any Ideas? Do I have a head gasket leak that is causing pressure to build in my coolant system??? Just inside the upper lip, where the thermostat seats, there is either a strange jagged casting seam, or some erosion of the block is taking place. Any suggestions appreciated. In fact, if someone can provide me with the solution that gets me home, I'd send them some salmon!!! Takers? Matt S