The amount of sealant you need to pour into the radiator will vary by the product. Each sealant contains different compounds. You need to check the label and read the manufacturer's guide to know the amount of sealant required. Usually, the dosage recommendation is mentioned in the package. If it is not mentioned, contact the seller or discuss it with an automobile expert. Basically, the experts recommend dosage according to the severity of the leakage and your model. If you observe the giant pool of liquid under your vehicle, then you might need multiple applications for a stronger mesh. It is better to purchase extra products in advance so that you will have the sealant handy if needed.