my temp before would usually stay right at 210 a little above or below...
now it seems to jump down to about 160 and come back up to 210 and come back down again i replaced it with a stock temp thermostat is this normal?? or do i have a bubble in the system still??

 

still got bubbles jack up at the rear pass axle and let it bubble out

 

exactly what i thought thanks!

 

Yes, the Renix (87-90) are more susceptible to air in the system when doing any cooling system work.

Burp it.

 

I would suggest doing the open system swap. Someone managed to eliminate the pressure bottle with a pipe that held a fitting for the radiator cap, and then they installed an overflow tank somewhere. Viola! No more bubbles lol.

Btw, I have the same issue with my '91, except its due to the VA cold weather and my 2-row rad upgrade. When the t-stat opens at 195, it will drop down to 170-ish and then warm back up. It repeats a few times until the temp stabalizes.