I have a 1997 Ford Explorer with the 5 speed automatic transmission and 4.0 ohv engine. There is a loud thumping sound coming from under the hood once it heats up. The guy I bought it from said it was the air vent doors? I hear it in the cab but it is much louder under the hood when I open it up. I can even feel the thumping in the radiator support and radiator hoses. Funny thing is, I can feel it hardest and loudest at the thermostat housing. Also, the air blows from whatever setting I set it to. That in itself tells me it shouldn’t be the air vent doors (flaps)It continues after I shut the engine off and it cools down. All I have done so far is burping the cooling system as the temp gauge would rise and fall quite a bit. It still does to a much lesser degree. But that thumping is strange. What do you think Scotty? Could it be the air vent flaps? Or is my suspicion of the thermostat more likely? Or do you think it could be something entirely different? Let me know if you need more details.
Well if you can feel it in the thermostat housing. That's how you got some kind of overheating problem going on inside the engine. I would start by removing the thermostat and just see what happens that could be blocking flow. Or you could start to be blowing a head gasket. Check my video. How to tell if your head gasket is blown on YouTube. Start there
