What causes my temp to fluctuate. T idle for a minute it's at 1/2, then as I drive it drops to 1/4 or so. It's an 88 rebuilt and I know the 88's should read around 1/4. Could it be the manual fan or temp sensor. The engine is not overheating at all. Please advise.

 

Have you bled it?

I have similar issues if I have air bubbles in the coolant system. Air bubble gets stuck at idle, temp goes up, then I rev it/start driving, and the temp goes right back down.

 

Ok, I will check that. Afterall, i did replace my heater hose that had started to drip on me.