The temp gage will rise to hot and the heat will go to cold while driving down the road. After a couple of seconds the temp gage will go back to the normal position and the heat will come back on....but the coolant from the resevoir will be everywhere,any input
Changed:
Resevoir Cap
Thermostate
Flushed Heater Core

 

I had a similar problem with the reservoir tank overflowing all the time. I live in Florida so I didn't have the heat issue. With the heat issue sounds like maybe the thermostat isn't working properly. If it's not opening correctly you won't get good heat as the coolant won't flow right. Make sure it's installed correctly and it the right part. Also, I put on a new radiator cap because they can go bad as well. I ended up needing a new radiator fan motor as mine wouldn't come on. Once I got the car for getting too hot, the overflowing stopped.