I bought a duralast radiator cap from autozone and replaced it, but was still a little low on coolant. It looks to me like the rubber flap on the bottom of the cap was covering the port that allows pressure to relieve itself into the reservoir, meaning the pressure stayed in the system instead, breaking the plastic of the radiator.
Cons: pressure stayed in system
Vehicle:
Lexus
Mileage: 215000 km
