Had the SAME problem ! It's your Thermostat ! And it WILL leave you on the side of the Road ! I have a 1997 Ford Explorer XLT, a year and a half ago i put it in the dealership and told them to have at it, they changed out ALL the filters, belts, timing belt or chain, bearings, plugs and plug wires,PCV Valve, thermostat even though the one on it only had 20,000 miles on it, new shocks, new brake rotors and pads all the way around. I spent almost $3,000. and also had something on the outside of the automatic Transmission changed but it turned over 100,000 miles around last Christmas and it's still running like new, you just HAVE to keep them maintenanced !!! !!!I had an accident that left me crippled and rather than get rid of my old Explorer i let my brother use it so i put it in the shop and had them make it "LOT" worthy and then bought a NEW 2003 4x4 LIMITED Escape and they refunded half the money for the work they did on my Explorer for buying a NEW vehicle. the Escape turned out to be a LEMON !!! We're in the process of getting our money back or a 2003 Explorer instead of the Escape ! I LOVE Explorers !