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, Mon, 23 Jun 2003 14:45:18
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The big problem seems to be air entering the cooling system. Note that GM Standard Olde Fashioned design has a regular radiator with a regular radiator cap. Just like in the days BO (Before Overflow). Standard practice was a couple of inches of air at the top of the radiator. As the system heats up and the water expands, air is forced out the radiator cap - as it cools, air is drawn back in. Overfill the radiator, and some coolant gets forced out, acheiving the desired equilibrium.
Along the way, someone figured out that the top 2 inches of radiator weren't radiating! Perhaps they decided it's cheaper to make the radiator shorter and make sure it's always full to the top (with an overflow bottle to buffer the expanding and contracting fluid) or maybe they needed the space for a lower hood, or maybe they felt bad about coolant routinely deposited on the roadway. Anyway, the easy way is to just connect the overflow hose to a bottle.
Problem seems to be that this arrangement can result in air, not water, being sucked down into the radiator, past the cap. This air then might be circulated along with the coolant, scrubbing away the thin inhibitor barrier and allowing the metals to corrode.
Saabs at least since the 99 have featured a pressurized tank with a pressure cap atop it. There is no overflow tank, and no way for any air that gets drawn into the system to become mixed with the coolant and circulated. FWIW, Mrs. G's Olds "Shortstar" DOHC V-6 is very similar, while the previous olds, with it's antedeluvian pushrod V-6, featured the "traditional" design. And yes, the previous car did develop a little "brown sludge" in the overflow tank, while the new car (so far) and the Saab (so far) are clear and clean looking - if orange.
posted by 24.166.84...
, Mon, 23 Jun 2003 14:45:18
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