A similar question was asked on another forum recently and the consensus of opinion was to leave as it is, the reason being that the problem was cured by the new head gasket design which by now virtually every car has now been fitted. If you Google "MGTF front mounted thermostat"  you will come across some very interesting thoughts on the subject, unusually well thought out ideas on the three options ie keep as is, PRT or front mounted. The idea of the front mounted thermostat was to have that large volume of cold water in the underfloor pipes constantly circulating in the warm up process so that when the thermostat opened only the  very small  amount of cold coolant in the radiator entered the system and even that was warmed up on its journey from front to rear. It was that large volume of cold water entering the system that was the cause of the thermal shock. I estimate that there is about three litres of coolant in those underfloor pipes so there is a bit of science to the idea. The downside is the longer warm up time for both the engine and the occupants.

Read More...