Disco 200 TDI - Head Gasket failure at back of block, blowing to atmosphere on a 180k mile lump - put down to age. Still ran fine, just chuffed a bit...
Disco 200 TDI - Head Gasket failure - consumed it's coolant, so presumed cylinder to coolant blow. Stil runs, just needs coolant topping up occasionally
Disco 300 TDI - System pressurised, expelled coolant via the safety release valve on the header tank. Presumed Head Gasket Failure, but on replacement system was still gassing. New Head and New Gasket (obviously) saw it right again - presumed cracked head between exhaust and coolant.
Other common issues on 200's are crank damper disintegrating, stops drive to water pump and aux belt, so can cause overheating, and utimately HGF. Caught mine just in time. The other common one is timing belt failure but I havn't had that happen yet...
Mark