Rog raises a good point regarding just the 4/4 models with aftermarket aluminium rad. There have been several reports involving the greater efficiency of same ironically causing overheating particular on fast motorway driving.
The increased cooling seemingly delays the opening of the thermostat such that any sudden increase in power demand causes overheating which the thermostats hysteresis can't accomodate in a timely manner. The recommended cure from one of the rad manufacturers, was a lower opening temp thermostat. Another option was using the smaller aluminium rad used on cars with air conditioning to accomodate the extra rad.
Higher power Mogs and particularly Roadsters don't suffer from this issue at all.
