Chevrolet: temperature guage/ bleeding system, rad cap, temperature guage

Question
I have a 95 corsica 4 cylinder, just replaced the thermostat and coolant, I've got good heat, and the engine does not overheat, however the temp guage moves up and down while driving, does this mean I need to bleed the system, flushing the system is difficult as this car does not have a rad cap only an overflow bottle. thanks for the help

Answer
Michael
Hi  if you are not over heating, I would wait till the engine is cool than remove the fill cap on a level spot  and add coolant till full. it should be ok.and if it still does it I would  open the cap when cool than run till warm and add coolant till full, ok