AO Platinum Member
Join Date: Aug 2003
Location: London, England
They generally fail at the same time as the rad, but the over-cooling effect of a failed stat is masked by the lack of cooling from the failing rad, they balance each other out unless you get either a very hot or very cold day.
Many people want to do the minimum work, so only the rad gets replaced (often only when it has completely fallen apart, ie many months after it should have been done!), then with a fully functioning rad the car obviously runs cold for many months until the owner whinges about poor heating in the winter, at which point we all tell him he needs a new thermostat (and obviously should have done it many months previously...).
Audi TT 3.2v6 DSG
2012 Renault Twingo 1.2
xAlfa 156 Selespeed sp3 + Brembo conversion
Fiat Cinquecento 899cc