The water pump gasket had ruptured and was leaking water, the entire water pump needed to be replaced with it. When that was replaced, the mechanic accidently blew a hole into the radiator (something about not filling it correctly after draining or something, I was a little too stressed at the time anyway).
Since the water pump/radiator was replaced (May or June, not sure), it never overheated.
This began about 1 1/2 weeks ago. It happened once on my way to a birthday party (didn't really notice anything until we were almost there and the temp was already at H). Let it cool down, and checked the fluids and for leaks. Nothing. Issue didn't come back until Monday (two days ago) and now, it happens every time I drive any distance (still works fine for short distances).
Yes, I used a subaru one, and replaced the thermostat just yesterday (after the issue came up), it made no difference at all (still lasting about the same distance before the cooling system stops working).
So if there is any darkness in the overflow tank, that points to the gasket?
I do have a bleeder screw and I undo that whenever I need to fill. If it is an air bubble that is stuck somewhere, how can I get that out? Just park the car on a steep hill (nose up) and fill? Or any tips? Does it need to some tool like for bleeding brakes?
Thank you very much.