02 300M 3.5L HO-OverHeating
 

I have a 2002 300M 3.5L HO the other day it over heated to the red...I didn't notice till it set a code and dinged...
Luckily I was less than a half block from home...when I opened the hood ...I discovered a crack in the tank reservoir
spraying coolant...I got a replacement online changed it out and added some universal coolant less than half a gallon!
I did open the bleed valve while adding coolant it was a steady flow no bubbles, but now the car overheats under driving conditions very fast 10-15 minutes it's fine idling but driving it goes up past half quickly but if I crank the heat it comes back down to half, is there another issue or just air in the system

prob warped the heads

Heads and head gaskets are vert robust on the 3.5. Anyone that advises heads or gaskets first needs to learn how to properly troubleshoot and diagnose rather than throw parts>