Hey all, first post here. I've spent hours trying to figure out what's going on with my heater core (plus hours scouring the forums to find someone else with a similar problem). Long story short: I just rebuilt the top end of the Bronco and have worked out pretty much every kink. The system for the HC is straightforward:

intake directly to the HC (no inline valve); HC directly to the water pump (with an inline filler cap on a T and a T to the throttle body).

But I have no flow through my HC and the hoses don't warm up (never have, actually). I flushed and back-flushed the core and hoses with a garden hose with no issue- flow out the other side was great. I've also made sure the cooling system was full and burped. So I know it's not with the core. It seems like there is a block between the inline filler cap and water pump. I've come to this conclusion because when I start to open the inline filler, coolant flows out. I'm completely stumped as to how there could be a blockage at the water pump as the pump is newer and there are no other issues with coolant flow (radiator flows, no overheating, etc.). I'm trying to see if I can find out more info before I start tearing apart the water pump. Ugh...

Does ANYONE have any ideas or similar experience so I don't have to freeze my butt off this winter?

 

Most likely you have a clogged heater core, is your temp gauge saying good, the thermostat may be faulty if the motor does not warm up, but its not fridged temps now. If your heater hoses are cold the water is not flowing thru the Core. There are threads of your specific year vehicle to check out when you have time.

 

You could bypass the heater core with a male-to-male barbed adapter (and clamps) as a test.

 

So, was it the clogged heater core or the messed up thermostat?

 

Clogged water pump. The heater core port was plugged up with sludge.

 

That'd do it!