Valve cover gasket end up to resolve an heater issue

[Takimo]

Long story short, i always had that issue with my heater that, whatever temp a put between 18.5c to 32c it always feels like its 32c , no difference between 22c vs 32c... in the end i never repair this because all the BMW pro garage i went, they didnt point out the problem .... so i been living with that for the past 5 years..



so this week i went to the garage to replace a valve cover gasket and the grommets as well ... and guess what ? no more heater issue... i can now feel the difference between 24 vs 32 or what ever number....


so how a valve cover gasket replacement end up to resolve this heater issue... im curious, anyone can see how ???