2000 GMC SIERRA 6000 VORTEC W/AC . Installed new 186 degree thermostat. At idle, heater core return line is flowing only one cup of coolant in 22 seconds, reading 103 degrees with heater on full. What should flow be at idle/2000RPM? At highway speed, heater floor vent is only 96 degrees at max heat/fan speed. Air lock? What is the problem/solution?
Two things--first replace your cabin air filter.second reverse flush your heater core with a garden hose and that should remove the build up of material in your heater core and restore the flow,hope this helps
Testimonial: "Hello; I backflushed heater core, cooling system flush. Heater floor vent temp. went from 96 degrees to 140; Thanks for your excellent advice. Robert"
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