Just a few days ago, I was cruising home from work and I noticed the temperature gauge on my 1999 Mazda 626 was higher than usual. Once I got home, I confirmed my suspicion that the thermostat had stuck closed. Replacing the thermostat on my 626, which has the 2.0-liter engine, is not much different than most other cars on the road.
Thermostat Removal and Installation
The drain cock on my 1999 626 radiator was on the lower, passenger-side edge. On my 626, the thermostat housing actually connected to the lower radiator hose, not the upper, but the removal process was the exact same as most other cars. I slid a new rubber gasket around the edge of the new thermostat, and aligned the protrusion on the gasket up with the jiggle valve -- the loose-fitting valve on the outer edge of the thermostat. The thermostat housing bolts on my 626 required between 14 and 18 foot-pounds of torque.
I refilled the radiator with 50-50 premixed ethylene-glycol -- standard green -- coolant, and burped the system.