GMC Repair: 98 s-10 2.2, engine temp, heater core

Question
My 98 s-10 2.2 engine temp won't go over 100 so the heater and defrost doesn't blow hot. I checked all the fluids and changed the thermostat. Any suggestions??? Thanks

Answer
Hi
I would HIGHLY suspect the heater core.
You MAY be able to reverse flow and clean it out.
Feel the hoses going into the core....at operating temps, they should be VERY warm. If you can grab them and hold on for say 30 secs to a min or longer, it is the core.
Try to reverse flush it.
I Hope this helps
Pawl