Temp up and down
 

So now a new problem. I have noticed the my temperature gage keeps going up and down. It will go up to 210 degrees and then drop to about 150, then slowly go up again, then back down. Any thoughts.

I have just put in a new Radiator, and thermostat.

97 GMC K1500

Thanks Again.

Sounds like you got air the system. Needs to be idled with the radiator cap off and the air circulated out. Try that to see if it helps. Also turn the heater on full to bleed the air out of the heater core.

I agree classic sign of low coolant due to air or just not toppin it off.

Thanks guys your awesome. I was thinking I was going to have to replace the water pump before heading hunting this weekend. Hopefully this helps.