I have a 2002 Silverado 1500. Recently, the coolant reservoir started leaking so I replaced it. Since then, I no longer get heat from the heater. I asked some buddies who said they thought it was a air lock in the line that runs to the heater core. So today, I bought more antifreeze and a coupla heater hose clamps. I cut the line that runs to the heater core and there was no liquid in the line. With the line cut, I started the truck and it started pumping water thru the line. So I figured I must have let the air out and the coolant started to run again. So I put it back together by putting a piece of copper pipe in where I cut it apart. Then I started the truck up again to let it heat up. Still no hot air out of the heater. I felt the line, could feel coolant running thru the line and the line got hot. But no hot air from the heater. My neighbor thinks the thermostat might be stuck (and it well could be,) but does anyone here have any other ideas?

 

after coming up to temp; if you bring the engine up to 2000rpm do you get heat?

probably still air in the system. Vacuum filling is the recommended method to fill vehicles.

 

take cap off radiator, squeeze the top radiator hose slowly repeatedly to evacuate air out because air will sit at the highest point. add coolant when needed. i've had to do this to my gmc after radiator install and my buick after replacing the water pump

 

With the truck at temperature touch both hoses going to the heater. If only one is hot then you have a clogged heater core. If they are both hot then you could have a bad blend door actuator.