this winter i have found that my truck's heater core isn't flowing, meaning i have hot on the upper hose and the lower is luke warm and there is no heat while running down the road. I have changed the t-stat and the heater core and radiator are new as of four years ago. last year i could roast a chicken with the heat. i also have no pressure in the radiator hose at all, engine runs at normal temp, no over heat situation and i don't smell any loss of antifreeze.

advise?

1999 f-150 4.6 150k

 

What is the coolant level in the jug?
Good luck.

 

with in a finger touch from the openning

 

For the lack of heat, it sounds like an air lock in the heater core if no good coolant circulation is taking place.
For pressure it may be the cap needs replacement.
Good luck.

 

how to bleed the air lock from the core?

 

I have a TEE in the highest heater hose and open the cap to vent out any air as I install antifreeze.. They sell these TEE to flush system with a garden hose.

also, some here have talked about water pump failures on the 4.6 motor... if you have no flow.

 

is there a valve on one or the other lines going to or coming from the core? if so, where would it be located??

 

some of the 4.2 or 4.6 motors had a vacuum valve on one heater hose. It should be at the motor end of one of the hoses, and have a vacuum hose going to it.