If your stock radiator for your Geo Metro doesn't provide enough cooling capacity, you're going to be running hot at highway speeds or the stop and go driving situation in the city. A radiator that may have been sufficient for a stock setup often can't keep up when you start making some serious performance modifications. Or when it is already damaged, any normal driving would still cause it to overheat. A radiator is designed to transfer heat from your coolant and water mixture to the air passing through the radiator. Both copper and aluminum radiators transfer heat quite well.

The biggest difference between the two materials is weight: Aluminum radiators can weigh substantially less than their copper counterparts. Geo Metro would rather be fitted with a lightweight radiator to not increase the payload, which in turn can decrease power. If your Geo Metro is experiencing overheating problems, its time that you have your radiator looked at. Overheating can cause serious damage to your engine. Having a replacement radiator installed for your old one is far less expensive than major engine repairs.