[Nevadan]

Here's a few posts about the cooling system I made in 2013:
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Here's some data from the "SAE paper 790206" - "New 5- and 6-Cylinder VW Diesel Engines for Passenger Cars and Light Duty Trucks" paper published in March 1979.

"The ratio between crankshaft and water-pump speed was raised to i = 1.1 (i = 0.85 in the gasoline engine). This results in a cooling water flow of between 140 and 170 liters per minute at rated speed, depending on the cooling-system flow resistance curve." (converts to 37 to 45 gallons per minute!)

That sounds like a lot of water moving through the engine.

My observation of the importance of a GOOD working thermostat is that when the engine is warmed up the back end of the thermostat must close the flow coming out of the block in the position right behind the thermostat, thus forcing all the fluid flow either out the back of the block or up through the water outlet on the head. The suggestion to use an 80C thermostat is probably a good idea since it opens sooner and thus closes that water flow coming out of the block. (I'm not convinced a cooler thermostat is better; as long as an 87 degree thermostat is working properly it will fully open and thus close the opening in the block. The hotter thermostat also allows the engine to generate enough heat for the heater during the winter.)
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On a trip a few days ago (September 2013) I drove over Donner Summit (Labor Day trip with temps at 95F in Sacramento and about 75F at the 7,200 ft summit) in 5th gear (4th plus overdrive) pretty much running as hard as possible. I wasn't towing anything and I'm using an 80C thermostat and a new radiator. When I got to the summit I pulled over at the rest stop and as fast as I could, felt the radiator temperature on the inlet and outlet sides. It was very hot on the inlet side and almost cool on the outlet side. I could place my hand on the plastic side of the radiator so it was probably no more than 90F. My conclusion: the radiator can handle all the heat the engine puts out; increasing the hot water (coolant) flow out of the head (especially the back of the head) would help.

I have to imagine the engineers that designed this engine had all the heat generation and cooling numbers at hand. They must have tested this thing under full load in hot ambient temperatures. There's a video somewhere on the internet showing a Pinzgauer running "wide open" in desert sand. If the cooling system can handle that type of heat generation.........