[W126 Coupe] 420 SEC coolant system problems

[Chet Hwilka]

Oisin,

In addition to what Dick said concerning the lower end, when there is a
breach in the gasket between coolant or oil galleys or even the combustion
chamber, coolant will flow through that breach and cause the cylinder head
surface to erode.  Minor erosions can be filled and resurfaced, but if it's
too bad the head will have to be replaced.

To give you an idea what's involved:
http://mywebpages.comcast.net/chwilka/cylinder_head_removal_and_replac.htm

Chet