I went in to work this morning. Kind of a chilly without a coat so I put the heat on a bit in the truck. As I was pulling into the ramp I realized that there was no heat. I looked at the gauge and it was in the middle. I felt the air coming out of the vent and it was cold. DOH! So I pulled into the ramp and opened the hood. I squeezed the main hose to the radiator and it was not pressurized. Hmm.. I wiggled that cap on the radiator and it was on the safety and not sealed. I think (am hoping) that the water just evaporated slowly over time and that there are no leaks. I never saw steam or puddles, and I did not smell it coming off of the core. I put some water in it and drove it home. No leaks. But I did notice something a bit odd. Yea, if you look close at the picture (click on it to enlarge it) you will see that the guys that worked on the truck a while back left a clip board on top of the 318. After they worked on it I was driving home and noticed the hood was on the safety catch, and not latched. I remember wondering what else they forgot. I guess I know. I am going to call them Monday and see if they checked the coolant when they were working on it. That would explain the cap not being sealed.