How to flush heater core in 1999 gmc sierra - 1999 GMC Sierra

SOURCE: I replaced heater core in 1999 gmc sierra 1500 5.3

no,, the system works from a vacuum and has to be worked on in a service garage. sorry about the bad news...

SOURCE: I NEED TO KNOW HOW TO INSTALL A HEATER CORE IN A

You'll be going thru the glovebox. It's a pain and takes some time. lots of sharp edges and no light.

SOURCE: nipple on fitting on heater core tube broke off.

There is no replacing of the inlet outlets on a heater core. You will have to replace the heater core.

SOURCE: How do I replace the heater core in a 1986 GMC

Usually around $80.00 canadian............The core is located under the dash on the passenger side in the plastic duck work by the fire wall....Hope this helps.

SOURCE: flushing the heater core

I removed the hoses and took a air nozzle at low pressure and blew in the return hose connection of the core. A big chunk of paste like substance shot out then pure liquid. I put the hoses back on and tested it. Now its blowing hot!!!!!!!