OK, I don't know much about how to diagnose anything, and I can't afford to swap parts all over right now.

Coming home from work, I hear a hissing sound, then shortly thereafter I see steam out of the hood and the temp gage at max, pull over and shut it down. Hear coolant bubbling and there's coolant all over the front driver's side quadrant of the engine bay - not much anywhere else.

Call Molly and have her bring coolant, fill it up, start motor, quite a bit of coolant burps out. Call AAA and have the truck towed home.

Get it in the driveway pointed uphill, fill it up some more, start the engine with the heat on full blast. A little bubbling goes away pretty quickly. Put the radiator cap on. The heat never gets hot, but the temp gage climbs. Engine dies when you let off the throttle, and can hear bubbling in the radiator. No smoke out the tailpipe. No external coolant leaks.

Where to go from here?

 

Thermostat and look over hoses for one that might be collapsing

 

Thermostat x 2.

 

The heater not getting hot suggests coolant isn't circulating so maybe collapsed lower radiator hose or water pump problem.