By the way---i do not know you, so I am not directing this to be mean!
I do this to everybody, who is not "me"!
Did you install the thermostat prior to having this issue or after--even so, is it sitting with the spring down and pointy side up,
Have you had the heater hoses off and maybe misrouted them?
Really good one---are you full of radiator juice?
Is there any sort of "water switch" on the heater hoses---between one end of them, to the other. If there is, maybe its stuck partially shut. It might can be completely removed (now that it's winter time) and the hose replaced in full length or just the valve be replaced with a suitable coupler till you can do better!
Are they old and squishy, and maybe the water-pump is sucking the return flat?
Are there any kinks in the heater hoses?
I'm about to hit the hay--see you in the morn!
I will leave you with some thing to try
Take loose the highest heater hose on the engine--at same time watch the water in your radiator--is it falling as if you just bled the air from an air pocket?
If no results there, continue with this:
Connect a long heater hose from the water pump to the fitting in the engine (completely by-passing the heater core)how hot does this line get?
While that is loose, force water thru the heater core with a water hose---is it flowing freely from the open side?
Heck, if the water hose is connected to every heater hose in the system, (one component at a time) does it come out the opening on the other end of each component
That oughtta keep you up all night!
Saturday, January 12th, 2019 AT 5:29 PM