recently bought a 1999 for 150 v8 5.4 liter engine with 112,xxx. I though I found a diamond in the rough and was so excited. previous owner said water pump was just replaced and a flush was done. I drove the truck home about 45 mins and everything was fine. yesterday I drove it about 5 and it started to over heat. I stopped to let it cool down and check what was up. I thought I saw what looked like oil in the coolant but no coolant in the oil. after sitting awhile I drove the truck home (same distance) and it wasn't even close to over heating. could this be the head gasket? or something else in the cooling system...im a little lost on this one? going for a compression test on Monday