Mechanics

HEARTER CORE

2003 GMC Sonoma

Heater problem
2003 GMC Sonoma 6 cyl Two Wheel Drive Automatic 70100 miles

mY HEATER WILL NOT WARM UO IF FACT THE SYSTEM CONTINUES TO BLOW COLD AIR WHEN I HAVE THE LEVER ON HOT.

wHERE IS THE HEATER CORE LOCATED? IS IT HARD TO GET TO?
Avatar
Jbrasher
September 13, 2008.




Under the dash on the passenger side. Yes it is hard to get to. Try having it backflushed, the Dexcool the factory uses tends to plug them up causing low/no coolant flow

Tiny
Jack42
Sep 13, 2008.
IS A " BACKFLUSH" THE SAME THING AS A RADIATOR FLUSH THAT THE EXPRESS OIL CHANGE PLACES OFFER? WILL I LOSE MY NEW COLLENT IF THAT DOES NOT SOLVE THE PROBLEM AND I NEED TO HAVE MY CORE REPLACED?

DOES THE FACT I STILL GET " COLD REFRIGIRATED AIR" WHEN I TURN THE KNOB TO HEAT SHED ANY LIGHT ON THE PROBLEM?

Tiny
Jbrasher
Sep 14, 2008.
Yes it is the same thing. With engine hot, check both heater hoses to see I they are hot, if not there is a flow problem with thecore. You can remove the shields under the dash and locate the blend door actuator to see if it is moving when you select different temps

Tiny
Jack42
Sep 14, 2008.
It's likely your heater core plugged. Flush it out. Mine had little reddish rust coloured chunks plugging it---thanks to GM's wonderful Dexcool. I run the good old fashioned Prestone green coolant. Against the advice of GM of course. In any case, disconnect the inlet and outlet tubes on the firewall that goo to your heater core and flush it out with a garden hose. Simple.

Tiny
Robbiet
Apr 3, 2009.
You should be careful how much pressure is applied to the heater core with the hose, they dont like household pressure for very long

Tiny
Jack42
Apr 3, 2009.
Absolutely. Be moderate with the water pressure applied-I was going to mention that but thought it was understood.
AD

Tiny
Robbiet
Apr 3, 2009.

AD