Liquid radiator sealant is a simple solution to a leaking radiator. Radiator sealant will repair pin holes and small cracks quickly. When compared to paying a mechanic for the same type of service, radiator sealant is very inexpensive. A leaking radiator poses serious engine overheating and fire risks. A leak should be isolated and repaired as soon as possible once it is discovered.
Open the vehicle's bonnet, then remove the radiator cap. Ideally this should be done with the engine cool. Never open a radiator cap when the engine is still hot from use.
Pour the radiator sealant directly into the radiator, measuring according to the manufacturer's instructions. Usually the whole bottle is used.
Pour coolant into the radiator until the manufacturer's recommended level is reached.
Replace the radiator cap securely, then start the vehicle. Allow the engine to warm up and the radiator to circulate the sealant according to the sealant's printed instructions. Most sealants require that you run the vehicle for at least 10 minutes to ensure maximum circulation of the sealant to fill the cracks and holes.
Refill the radiator with coolant to replace any that may have leaked out while the sealant was circulating. Replace the radiator cap and close the vehicle's bonnet once these steps have been completed.
Allow the vehicle to rest according to the sealant's instructions. Many radiator sealants require that you allow the sealant to cure for 12 to 24 hours without operating the vehicle. This will ensure maximum adhesion and leak repair.
Radiator sealant is only intended to be a temporary repair. The plastic-based sealant will eventually allow the leaks to return, so a professional leak repair or radiator replacement will still be necessary in the future.