Actually it is a 2007 Ford super Duty 750. The STOP ENGINE light came on the other day, my boss said check the antifreeze level because there is a sensor in the radiator & if not full that light will come on. I put in a gallon of antifreeze & that did the trick for 1 day. Light came on yesterday & antifreeze level was down a bit, I filled it to full, ran truck to ensure it was circulating & it was. I then let truck sit for about 45 minutes then I had to go pick up my loads & guess what that damn STOP ENGINE light still came on, radiator still full. I ran my loads let truck sit overnight. Checked level of antifreeze 1st thing in the am & it was low, I filled it & that STOP ENGINE light came on and stayed on. So now what do I look for & tell my boss?