I have been searching for answers all day. My truck is an '02 Blazer with a 4.3. I flushed the radiator and heater core. I have heat, and my temp. Goes to about 180 and stays there. The top hose doesn't get firm and I can take the cap off and touch the coolant in the radiator. There is flow from the pump, but it seems weak. As this is my only vehicle right now, I really need to figure this out. Any help would be greatly appreciated. Thank you.

 

When I flush and refill the coolant I jack up the front on only the drivers side to purge air from the system.

 

The only thing I can suggest is to pressure check the system. When the coolant gets hot and the system is sealed, pressure will build. You must have a loss somewhere or also replace the radiator cap as they after time lose their capability of holding pressure. I just thought of the thermostat, if it were stuck open, in some vehicles the coolant doesn't have time to get hot enough due to the constant circulation.

Water pump must be functioning or otherwise you'd be overheating.