1998 silverado z truck
 

overheated since then thermostat up and down white smoke from tail pipe any advice on problem is appreciated tks:eek:

I had one do the same thing one time and it turned out to be a blown head gasket. I hope this is not what you have but it may be. Good luck.

Could be a bad thermostat... I've had few bad thermostats right out of the package. Make sure there is no air locks in the cooling system.

Welcome to the forum

White smoke out the tailpipe is the bad sign.