how to replace a thermostat on a 99 cougar 4 cyl..where exactly is the thermostat housing located?

Answer 1

Follow upper radiator hose to engine. At the end there's a housing where the thermostat is located. Make sure you put it in the same direction that your remove it!

Instructions with pictures located here:

http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/1b/c8/7d/0900823d801bc87d.jsp

Answer 2

Trace the upper radiator hose back to the engine. Where this hose clamps onto in the engine is the T-Stat housing, remove this hose and the housing and you will find what you are looking for.