Q: Coolant doesn't stay in tank

Greetings. The coolant reservoirs on your model vehicle usually produce leaks at some point. It is due to the fact that the reservoir itself is constantly under pressure created by the coolant system. The material it is made of is a plastic like material. Overtime, the plastic looses strength and becomes likely to exploded or crack under the system’s pressure. I suggest having a trained technician, such as one from YourMechanic, to inspect the coolant leak and determine exactly what the problem is.