Thermostat controls temp. It should only open when the engine starts getting close to the stats set-point. If it isn't getting there, either the stat is bad, or the install went wonky. Not losing any coolant are you??

 

Nope not leaking at all

 

Gotta be something with the stat. Coolant is either finding its way around it, or it is stuck open. Didn't get a safety-stat by any chance did you? They like to fail quite often.... (as they were designed to do... they are just too willing to do so.)

 

I'm not sure it's a safety one or not..it came with the plenum plate that one of the members makes.

 

i re-read your first post that says you already replaced the t-stat with a new one that you tested in hot water and it seemed to test out properly.

however, the truck is behaving like the t-stat is opening early, which prevents the truck from coming up to normal temperature.

an easy test is to let the truck cool down completely. release the upper radiator hose clamp at the radiator and push it back down the hose. disconnect upper radiator hose at the radiator to get it unstuck. now reconnect it temporarily (no clamp) and start the truck.
... water pump is turning and attempting to push coolant around.
.. t-stat should be closed.
... upper hose should have zero or almost zero amount of flow.

disconnect upper hose at the radiator and see if its pushing coolant out. be careful - you might get wet and DO NOT do this when coolant is hot.

if its pushing coolant out, your t-stat is hanging open and is no good.

 

why even put it back on(radiator hose) temporarily? Gotta be the stat. If radiator was clogged or pump going wrong way,or stat staying closed, would all cause overheating. Right?

 

i'm assuming his t-stat is stuck open and with hose disconnected the coolant is going to come gushing out. so with it temporarily reconnected he'll lose less coolant between the time he cranks the truck, see's the leak, and rushes to shut it back off

 

well i tested it today and here is 2 videos of the results....

when I stopped recording the first one I noticed this so I recorded some more...

I think that if the thermostat was stuck open, it would be putting out a lot more fluid than this.......What's my next step..

the fluid color was normal green until the last jug of antifreeze i bought that I have only used to top it off. It says it is a universal mix for any make/model ( sent the fiance to the parts store while I was changing the stat for the second time....

 

I personally don't use universal as I've heard bad things about it. Besides, green is usually cheaper anyway.

 

well hell. so much for that theory.
the dribble is normal.

ok, here's my next guess. on the top front of the plenum is the Intake Air Temp (IAT) sensor. I think??? that the PCM monitors this, and uses its reading of ambient air temperature to adjust its monitoring of the engine. so if its 90* out, it expects the engine to warm up quickly, and sets the 1281 if it doesn't. on the other hand, if the pcm thinks its -25, then it expects the engine temp to stay cold for a lot longer, maybe all day.

this may or may not be what's up, so take it with a grain of salt, but i think your IAT is misreading on the warm side. this can be checked with a scanner, or, if you can swipe one off a junker or buy it real cheap, consider just swapping it.

the tell-tale info is that you said it warmed up normal and had good heat in the cab, and that the t-stat seemed to open at the proper time, and the upper radiator hose got hot at the right time.


edit - i re-read your first post again. if the 1281 has only appeared once, reset the pcm and see if it comes back regularly. it might be a fluke.