Two choices in my book,
you either have a hell of an air block, or head gaskets!

 

Or plugged heater core

 

is it possible the thermostat is in backwards?

 

The quickest way to find out and to possibly correct the problem is to park your truck on an incline, front end high, take off the radiator cap and start your engine. Watch for it to start to heat up and bubbling in the radiator.

What you are doing is allowing the coolant to circulate yet also providing an escape for an air block, any air in the system will eventually rise up and escape. Once you see the coolant circulating and allow it to do so for a bit then just top it off with just enough coolant to close up the air gap at the top.

If that does not work then you have to look at other problems.

 

I'm siding with Primo on this one. I've seen a LOT of bad thermostats, new out of the box.

It's always a good practice to drop the thermostat into a pot of slightly simmering water to check it before installing it.

Always make sure the pointed end points at the radiator.

Check the bottom hose for excess pressure after it warms up by trying to squeeze it.

If you do follow the advise to let it run with the cap off on an incline...be very cautious of the engine reaching temperature and the coolant spewing out of the radiator.

 

Agree with others. Cant trust stuff just cause its new. Always check stat. Don't even like re-built pumps because sometimes they use the wrong impeller. But truck hot, AND no heat? Agree with air first.

 

Parking the truck on an incline to bleed the air is not really effective. If you want a better method, drill 2 small holes on the thermostat housing.

 

I'm having similar issue... Kinda... I'm lost I know that. My truck only overheats when hot outside. Heater core in n out hose both hot but no heater. Have flushed, new water pump, even took out thermostat. Why is it overheating? Fan belt driven. No leaks, oh yeah... Gurgling in heater core when push gas pedal (air in system)

 

just replied to another one of these. more times than you think its a bad intake gasket. ive chased down the problem before ending with bad intake gasket

 

Overheating --> clogged up radiator

 

Many possibilities. Start with renting a radiator-pressure-tester from one of the discount stores. Pump the cooling system to 16 psi and look for leaks. ALSO, use the adapter and check the radiator cap! It should pop at 16 lbs. Mine popped at 10 psi and caused many of the issues you mentioned. There is lots more to how this system operates than many people think.

 

Running hot but no heat

I just had the same problem with a Subaru, Radiator cap was the problem.