97 ecsb 5.7L Vortec Overheating Issue!?!?

[TLoud]

So lately when I've been driving for about 5-10 minutes or so my temp gauge goes up and check gauges light comes on. If i crank the heat on high and give it a little gas it usually will start to fall back down and sometimes even drops way back down close to 100. I replaced the thermostat today thinking this might be the quickest and easiest fix but no luck. Still the same issue. When I'm idling at a stop light and have the heat on it blows cold, but as soon as i step on it, it starts to get warm again.

I'm thinking either water pump or heater core... what do you guys think?

 

[Wwildman]

Have you checked the coolant level ? Also the rad might be blocked or plugged up

 

[JonZ71]

Does your upper and lower hose have different tempatures?

 

[TLoud]

coolant level is full, and yes when first started the hose going to the thermostat is colder but as soon as i turn the heat on it starts to get warmer..

 

[JonZ71]

sounds like a water pump. is it leaking at all?

 

[TLoud]

nope thats why i was thinking maybe the heater core is plugged?

 

[JonZ71]

or the line is plugged. on your passenger side floor board youll see a plastic black container thing start your truck and put your hand underneath it, if it gets warm, heater core may be leaking. prolly wouldn't be a bad idea to change it anyhow.

 

[TLoud]

yea except heater cores are expensive as hell and are a ***** to replace...

 

[GMCTRUCKS]

Flush the core with your water hose just disconnect both hoses and flush it out.

 

[JonZ71]

they are? i changed mine out in a half hour and it was like 50 bucks...