Quote:
Originally Posted by v8volvo
Cool!! 
Regarding cranking up the heater in order to pull more heat out of the coolant -- in many other cases this might help to some extent, but in the particular case of the D24/D24T cooling system, I think this tactic is unlikely to have any constructive effect and, in fact, might be *counterproductive* to keeping the engine cool. Times when I have tried it, it hasn't had any noticeable effect (other than making the driver very uncomfortable...), but the D24's cooling system layout makes a negative consequence possible. Since it's an unusual setup where the thermostat is located in the coolant *return* path from the external and internal circuits, on the suction side, rather than up high in the cylinder head outlet to the radiator as it is in almost everything else on the road, the thermostat is exposed to flow from many circuits -- not just what's inside the motor, but also the oil cooler return, IP cold start t-stat return, heater return, radiator return, etc. Some of these circuits, where heat exchanger matrices are involved, involve a temperature differential. Cool fluid from the radiator return doesn't flow past the thermostat's wax pellet since it enters from the front of the t-stat, but cool fluid from the heater return *does*. In a system like this, if you crank the heater up and start extracting a lot of heat out of the heater core, you start blowing a lot of coolant across the thermostat's wax pellet that is significantly cooler than engine (and especially cylinder head) temperature. Next thing that happens is that the thermostat begins to *close*, even in the case of an engine that is working hard to climb a grade and producing a large amount of heat, and begins recirculating hot coolant through the motor and restricting flow through the rad. Not a good thing...
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Good observation. I never thought about that!
On a trip a few days ago 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.........
What about using Evans coolant?
I'm beginning to think overheating and warping of the head is only caused by coolant loss.