Hi,
I have a Mazda 3 2004 2.3L four door.
Recently I noticed that when I start driving after a couple of minutes, maybe four or five...my fan start to go non-stop, I can hear it from inside, then after a few more minutes warm air start to come out from the vents (normal) but when I stop on a traffic ligh for a few seconds the air start to go cold....then when the car is back in motion the air goes back to warm again ( as it should be).

If I stop the car and open the hood I can see the fan still going and the antifreeze reserved container is to the top and very very hot and I can see the pressure on that antefreeze container is a lot.

I do not have any engine light on yet but a friend told me the the thermostat maybe the problem, so I went to the dealer bought one and replaced it myself, then fill up the antefreeze container as it should be but the problerm came back again.

Can someone please let me know if there may be something else that it is not working propertly and if I should be replacing other parts?

Thank you!