HEARTER CORE

2003 GMC Sonoma

Tiny

jbrasher

September, 13, 2008 AT 7:48 PM

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?

FOUND 4984 RELATED QUESTIONS

No Heat

37 ANSWERS
5 IMAGES

6 Answers

Tiny

Jack42

September, 13, 2008 AT 8:58 PM

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

jbrasher

September, 14, 2008 AT 8:04 AM

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

Jack42

September, 14, 2008 AT 8:28 AM

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

robbiet

April, 3, 2009 AT 1:50 AM

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

Jack42

April, 3, 2009 AT 9:07 AM

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

robbiet

April, 3, 2009 AT 3:24 PM

Absolutely. Be moderate with the water pressure applied-I was going to mention that but thought it was understood.

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