M25 Thermostat
It should begin to open at 160 degrees and be fully open by 180-190 degrees. If you put the thermostat in a pan of water with a meat thermometer and then heat the water you should see it work within these parameters. If you are sure your engine temp guage is working correctly you should see the temperature rise steadily towards 160 and then drop when the thermostat opens and then settle in at 160 to 180. I was having overheating problems so I replaced the thermostat and it did no good but when I installed a larger heat exchanger the system now works as advertised. Tim
