Fan not working and car overheating.
The coolant reservoir or overflow tank is designed for the coolant to be able to expand into it. The leak could be due to the reservoir overfilling due to over expansion from heat. If the fan is not working, that could be related to your over expansion of coolant problem. This may also cause overheating of the engine. If you suspect that the fan is at fault, I would recommend having a professional from YourMechanic come inspect and diagnose your issue. If the fan tests bad during the inspection, have it replaced as soon as possible as it is certainly the cause of your over expansion issue.