This weekend I heard what was undboubtedly my favorite "Car Talk" call to date. The woman in question was calling from Pennsylvania, but spends much of the year in Botswanna as a behavioral zoologist studying baboons.
Botswana, it seems, suffers an extreme rainy season where a good portion of the southern savannah is under water for months at a time. Even when the waters begin to recede, this area isn't even remotely navigable by anything less than a "serious vehicle".
Our entripid zoologist finally made such an investment: the Land Rover Defender. Let's give some credit to British Motors, here, folks: "Defender" is, without a doubt, the coolest name possible for an SUV. It conveys everything you want to convey about ruggedness and durability without aggressive or pretensious overtones. Someone in marketing should have a salary for life just for thinking of that name. Like all good marketing ploys, it seems so obvious that you tend to think, "oh, anyone could have thought of that" until you notice that for years, no one did.
Anyway. The particular feature that made the Defender so desirable was the optional snorkle, which should enable the Defender to continue driving even when largely submerged.
The operative word here is "should".
Apparently the fine engineers at British Motors must have dunked a Defender in a tank of water with the snorkle hooked up, revved up the engine, and verified that the engine still worked. It seems they never tried to actually drive anywhere.
If they had, then they would have noted that while the snorkle works fine, the force of water passing through the engine block area as the vehicle moved forward tended to push back the fan blades into the radiator, thus shredding the radiator. This will happen, apparently, in anything more than 21" of water.
The advice of British Motors: don't drive in more than 18" of water. One wonders if a snorkle is actually required in 18" of water.
Native Botswanans, who spend a good portion of the year travelling around in significantly more than 18" of water, have come up with a different solution: before entering water, take a piece of wire, and tie down the fan so it won't rotate.
This reminds me of a great quote from Jared Diamond in "Guns, Germs, and Steel" in which he says -- I'm paraphrasing -- that the notion that indigenous peoples have remaned technogoically backwards indicates lesser intelligence is ludicrous, that if anything, common sense observation shows them on the whole to be more observant, more innovative, and just plain more clever than their lazy western industrial counterparts.
Which leads me back to the woman's question for the good brothers at "Car Talk": just how long can a Defender drive around in the water with the fan tied down before overheating?
The "Car Talk" answer, in vintage form: the only function of the fan is to dissipate heat. Submersion in large bodies of water does this much more directly and effectively: "you're using the whole river as your radiator." Their advice: minimize time spent tying and untying the fan by driving everywhere underwater as much as possible.