No heat

i just put a new heater core in my 1997 silverado now no heat,the pickup heats up as usual,the blower works the air comes thru the vents, the defroster, i can hear tthe doors close or open in the box,the hoses from the engine to the core are hot but no heater or defroster. do you have to “burb” these as some of the other models i have worked on? can you help me out? the truck’s my mother-in-law’s and getting it from both side and it’s not good i need your help!!! thanx,sam

Thats a tuffy. If the hoses are hot the core should be hot. Hmmmm. Maybe try purging the core with the old garden hose trick. Post results.

There may be air trapped in the heater core. To purge the cooling system of air do the following.

Get the engine up to operating temperature. With the engine idling loosen the upper radiator hose clamp. Take a small flat bladed screwdriver and slip it between the upper radiator hose and the radiator hose neck. Allow the engine to continue to idle until all that comes out of the upper radiator hose is coolant. Remove the screwdriver and retighten the hose clamp.


What was the reason for replacing the core, no heat or a leak or???

You mention the doors so I suspect you know there are two doors; a diverter and a blend door. The blend door should function when you move the selector between cold and hot air.

If both hoses are HOT, then coolant is moving through the core even if there is an air issue. Should at least have some sense of heat but if it’s stone cold, I’d be suspicious of the blend door. The motor gear may be stripped even though you hear the stepper motor running…

done this once, park nose up on a STEEP hill. (or up on ramps, etc) pop the radiator cap (dont get scalded) monitor the coolant level, while reving the throttle. if you are still getting warm hoses, but no heat at the core, check to make sure the hoses are warm coming through the firewall. as TT mentioned, there is a diverter valve in the hoses, near where they split to go back into the heater core. if this diverter valve is stuck closed, no amount of heat will go back to the heater core.

The earlier question is pretty valid. why did you replace the core? how did you trouble shoot that was the problem? any water on the interior floor? antifreeze residue coming out vents? or was this just a no heat issue? b4 making other assumptions have to make sure original problem was diagnosed properly.

Sounds like air in the system . . . Tester has a good method which he has already posted. I have a purge screw on my cars presently . . . you just crack open the screw which has a hole in the head, close it when the air stops. Sometimes it takes a few tries, air can get trapped in weird places, I guess. Did you have heat before you replaced the core? I almost don’t want to ask . . . but could you hook the hoses up “wrong” on this application? My bet is on the trapped air. Good luck! Rocketman