When the coolant reaches the cold fill line, close the lid and tighten it until you hear it click
If you check MOT history of a car, a common MOT failure is low coolant which leads to an overheated engine. Not only will an overheated engine fail the MOT, but it would also lead the engine to totally fail.
Complete a MOT history check online and have any radiator issues resolved beforehand to avoid the extra hassle of a MOT failure.
What causes a radiator to crack?
Overheating or high coolant pressure within the radiator might lead to a crack due to a faulty thermostat or a leaking head gasket. The Radiator's ability to be cooled by outside air is hampered by the summer heat. Overheating and a cracked radiator can occur if the radiator fluid is not maintained.
My radiator is empty, but my reservoir is full
A burst head gasket is a typical reason of the coolant reservoir being full yet the radiator being low on coolant. One of the cylinders' combustion gases seeps into the cooling system, forcing coolant from the engine into the reservoir. When the reservoir is full, the remaining water overflows into the sea through the overflow outlet.