The coolant should be between the "Full" and "Low" marks on the coolant reservoir when the engine is cold. If the coolant is low add sufficient coolant as specified in your owners handbook. Do not overfill your reservoir.
Warning!
Never attempt to remove the coolant pressurised cap when the engine is running. Doing so might lead to cooling system and engine damage and could result in serious personal injury from escaping hot coolant or steam. Turn off the engine first and wait until it has cooled. Even if the engine is not operating, do not remove the pressurised cap while the engine and radiator is still hot. Scalding hot coolant and steam may still blow out under pressure, which could cause serious injury. If you need to continually top up the coolant level, or if there is any discolouration
of the coolant, consult a TACC member workshop immediately to try and avoid expensive cooling system failures.