Well, made it to the shop with the mini van and started looking. Heater hose under the dash were both hot and the blend doors worked. Opened the hood to do some looking and found some red residue on the tank under the fill cap. Scraped it off and found a small crack in the tank. Opened the cap and no water was visible. Filled it up with about 3/4 gallon of water and heater works great! I kept the coolant reservoir filled in the Summer and Fall so it did not leak out fast enough to get engine hot. That is why the heater worked on the last trip we took in about Oct. Lucky it did not get hot. My wife never watches gauges. Got lucky this time. Now for a new rad. What kind of coolant is this special stuff it says to use on the overflow tank? Or should I just use the old Prestone stuff?