for most latest car and SUV model it is located beside the radiator. You can find it easily by following the overflow hose attached in the neck of the radiator. the end of it is the location of the...
Tough to narrow it down with such little detail, but it sound like your car's thermostat may be malfunctioning and not controlling the temperature correctly.
it is normal, when the coolant is hot and pressure built, the pressure cap allows the coolant to drain to reservoir to reduce pressure in the cooling system
But, if it continually does this whereby...