[CHANCE1234]

I would guess, thermostat as well, sometimes they get clogged with sand and seaweed. The way to best check to make sure they are opening at the right temp is to remove them from the engine, and put them in a pot of water at about medium temp. With a cooking thermometer monitor the temp and around 140 or so check them to see if they open. you will have to take them out of the water momentarily to check the gap. Hopefully this helps.