Description Reviews MINI Cooper S Thermostat Housing. We used to replace them all the time when doing a thermostat just to make sure that we had the problem fixed; but after some testing we found that the housing is not failing, just the gasket was. If you have a really bad leak, and there's lots of crusty dried coolant around it, you may want to replace it all to help the clean up. The housing has brass inserts that corrode when exposed to lots of coolant. Most of the time we are able to clean up the current housing, but you will have judge how bad it is.