I recently replaced my radiator as a decently long crack appeared across the top of the old one. The car never overheated or got close to being hot. I checked the oil and there are no symptoms of a head gasket going bad. Temperature also stays steady when at optimum temp so I'm guessing the thermostat is fine. Just wondering what the cause of this could be? Someone I know thinks there may be a pressure buildup that caused the crack. Is it simply because it's a 17 year old part? I replaced it with a mishimoto radiator and would rather that not crack due to "pressure buildup" aswell.