Hi John,

They can develop a few rattles and hums (not as musical as it sounds...) that are relatively cheap to remedy. Things that'll cost more to fix including damaged front side airbags (there will be a warning light on), worn sunroofs and a whining from the engine on cold-start caused by lack of oil supply, which necessitates replacing the oil filter housing. The automatic transmission can give trouble too.

Otherwise the Cooper is pretty robust.