Hi guys, so I came across an issue yesterday on my 2016 wrx sti with 26k miles. I noticed my temp gauge was at 3/4 of the way while driving, when I stopped the gauge went down one small bar above normal temps, i turned the car off to let it cool down a bit. After 10 minutes I started her up and hit the road once again, after I got home, I started backing up into my garage and it started to overheat again slightly lower than 3/4 of the way. I turned off the car and checked for coolant leaks or ruptured hoses and found nothing. When I was going to check the coolant level I noticed that I?m missing the whole overflow tank? From my understanding I know that the overflow tank is only used to store excess coolant from the system, so I?m not convinced that it?s the cause of the overheat. I ended up trying to add some coolant from the top cap, but it wasn?t even low, I checked to see if the thermostat might be bad but it seems to be working properly. I also checked to see if I might be low on oil but Im also good on that. Any help would be appreciated since this is my first Subaru and I only have about 6 days with the car. Thank you!