Today, I flushed my heater core. I removed the hoses going in and out. I ran water both ways 5 times each until everything came out clear. Then I ran air through the hose going in. First at 20 psi, the 40, then 60.

I have warm air now, and both hoses are hot to the touch, whereas before the out hose was cool/barely warm.

The problem is, the air still doesn't stay warm for long, and after driving a little while warming it up, parking it for 5 minutes the temp guage goes down to halfway between 200 and 130. The temperature goes back to normal after driving for a couple minutes, and goes down when idling aain.

What are the recommendations for the heater, and what did I do to cause the temperature screwup? Maybe run clr through next time?

 

I'm suspecting the thermostat has failed, hence the reason for the fluctuating temperatures.

 

My grandpa went out there and burped it, the temperature is okie dokei The heater is warm, and consistent on recirc, but not hot. Should I run CLR through or up my pressure when I blast air through it. Thanks in advanced for any more help.

 

The heater core is most likely clogged. Even if you get clean water coming out, it doesnt mean some of the tubes are not clogged/restricted. And I wouldn't blast it out with too much air pressure, or you'll blow a hole in it. The heater core is a very common problem on these trucks.