MY 2000 Ford F150 4.2L v6 is running cold. I bought it this summer and it ran a hair above the cold line on the temp guage. Now that it is cooling off it doesn't come off the cold line. I have drove it for an hour and it never move. The heat is barely warm. I thought it may have been a stuck open thermostat so I changed it out with a 195 and it did not help. I can let the truck run parked for 15 minutes and still be able to grab the hose leading down to the thermo. Any ideas as to what is wrong? The guy I bought it from used it to pull a small boat. He said it started running hot when he would pull with it so he had a new radiator, thermo and clutch fan installed. Then he said the truck ran on the colder side. Now the thing just runs plain cold! Please help.

 

Okay so I disconnected the top radiator hose from the radiator after it had been sitting for about 5 hours and turned it on to see if the t-stat was working. About 2-3 second later coolant poured out. Does this mean the t-stat is stuck open? What else could be wrong? I know the truck was ice cold when I started it so no coolant should have come out of the hose.