The cap of the coolant tank broke down, so I bought an original gm one and replaced it. What I have been noticing, that had never happened to me before, is that the water raises to the cap of the tank. The car does not overheat or do anything strange, though. When I stop it and check the coolant, I can see it go down until it remains a little bit higher than the maximum. Is this normal? I've never seen this before; the normal level used to be maintained.