I have a 95 Mazda Proto with a 1.5 motor, 108K miles. I have been having probles with it overheating on me. I replaced the thermastate. Then I noticed that the ratiator fans were not running so I traced it back to the cooling fan sensor. I replaced the sensor and now the fans run when they should, but I am still overheating. I have heard that the ratiator cap has to hold a presure and if it does not then that can be the problem, is that ture and what else could the problem be?
Since you know how to replace a sensor-buy yourself a coolant pressure tester-it will help find your problem or a bloc check. Possibilies: water pump, blowngasket, clogged Rad, collaspe hose, bad stat.
Check your dipstick for milky color and white smoke from the rear of he car.
Or disable the ignition, disconnect your upper hose from the Rad and see whether the pump is working-it should push coolant out.