Where is the thermostat on a 1991 Ford van 4.9 liter?

The thermostat on a 1991 Ford van with a 4.9-liter engine is located in the engine's thermostat housing, which is situated at the end of the upper radiator hose where it connects to the engine. To access it, you'll typically need to remove the upper radiator hose and the bolts securing the thermostat housing. After removing the housing, you can replace the thermostat. Always ensure the engine is cool before starting this process to avoid burns.