well,i've discovered another piece to this riddle.after towing last week and it started running warm again,i got home and pulled it in the shop,never touched it until sat.i raised the hood and the top rad. hose was collapsed.replaced the hose and got to thinking,the overflow tank is s.s. round canister with no vent and the hose just goes onto a fitting on the top,it doesn't go down into the canister.may or may not be a problem,not sure at this point.