I hear what ya saying bout thermostat it gets hot quick and runs hotter than it used to I did have a standard header tank on it and did the same then that's why I thought I'd change it
Aswell the amount of times iv bled the system and been out in it I would have thought the air lock would have cleared
Guna do compression test
Sniff test and pressure test 2moz nyt to see if anything comes of it