is there a bleed point on the coolant system anywhere? Hopefully on the head somewhere? I recently changed a lot of hoses and replaced the coolant. I was quite surprised when it seem to just fill fine from the radiator cap. But after a long trip it over expanded in the tank and leaked out, the hoses felt like they had air in them I got some of it out but am sure there's still some in there.
Gtir Motorsport club