For those of you thinking about this one route to go is to have your radiator re cored. They do "silt up" after a few years and back flushing etc helps but will not cure the problem
I have had two radiators done this way, one for my BMW 2002tii and one for my rally car. In both cases I went for larger capacity cores
In both cases they have worked fine, the BM in stop start traffic runs at "normal" all the time and the rally car is "cool" even after a stage.
Companies like Serck Marston in the UK have a recoring service
And finally before blaming your radiator make sure that
Your antifreeze is good
Your fanbelt is at the right tension
Your fan is not damaged
Your water pump is in good shape (bearings, impeller etc)
Your hoses have not gone "hard"
Remember MB and other companies do test cars in extremes of temperature so the system is designed to cope with a wide range. However thats when its new
Malc