Recently purchased this truck and have only put about fifteen miles on it. (I trailered it home from where I bought because is was a couple hours away). This truck is an auto with 121000 miles and 4x4. The first time I drove it, the engine was surging a little bit and the truck also over heated. I ran the codes with my scanner and came up with IAC and TPS being bad, as well as lean and rich codes in bank 1 and a couple others. It overheated for a few minutes and then the temp rapidly dropped to around normal so I decided it must have a sticky thermostat. I changed the thermostat a week ago and drove the truck with no problems for a couple miles. Had to go out town so no time to mess with the tps. I got around to the IAC and TPS today, started the truck and it ran great with no issues for around 15 minutes. I ran the KOEO codes and got the system pass code. I performed the KOER codes and as I was letting the engine idle it overheated to max out the gauge. Water pump was extraordinarily hot. The codes that came up were HO25 sensor and Coolant temp out of range. Now it won't start at all. I let it sit for about ten minutes still won't start. Checked radiator cap and had pressure and warm antifreeze there, checked oil and dipstick was hot but no antifreeze in it so I don't think I popped a head gasket. Key on engine off shows the temp gauge has gone down just passed the halfway mark on the gauge. I know it still has spark, and the fuel pumps both are still working. Have not put a gauge on the fuel rail but is has pressure. Wondering if I need a waterpump, coolant sensor, and maybe another thermostat? I know that's long but wanted to give all the info I could. I'm in bad shape here, I'm depending on this truck. Thanks for any help. UPDATE: I let it sit for over an hour, and also unplugged the engine coolant sensor and it started right up and idled perfect. Still thinking waterpump and sensor. Any thoughts?

 

Could be a lot of things going on here from a clogged rad to a bad waterpump, trapped air pocket or even a blown head gasket. I suggest you start it up with the rad cap removed and let it run until you can see water flowing through the rad, if that never happens and the temp goes high then change the water pump and try again.

 

I'm with conanski here. Also you might try the test without the thermostat in. If it flows, then try it with a new thermostat. New doesn't always mean good when it comes to parts, but it usually does.

 

Squeeze the bottom hose & see if it has a support spring inside it. Particularly if the hose is not original. No spring?, then see if it is collapsing when it goes hot.

You can also drop your your t-stat in a pan of water hung on a wire with a thermometer, bring up the heat & check opening temp. Should open at 195*.

Lastly I would check the fins of the rad. Recently had mine out & was shocked to find out how much crud was packed into it. Don't see how it passed any air at all.