Expansion of tubes

Here is a radiator that has had the tubes expand and in turn crushed the fins which stops air flow going through.
Not a common thing but however it does happen.

This can happen by the radiator having too much pressure in it and the radiator cap may not be able to release or the head gasket may have blown. The expansion of tubes means that the air flow is restricted and your radiator will overheat. 

Not to worry though, Muirs Radiators can supply you with a complete new radiator and and radiator cap and you will be on you way in no time.