Volvo MD11C Overheating
I have the same engine, but it was converted to fresh water cooling several years ago. Still, last summer it was overheating, but I could run it at about 1000 rpm for some time. To make a long story shorter, one of the (three) internal ports between the exhaust manifold and the block was clogged. So a thorough break-down and cleaning seems in order for you.