Quote:
Originally Posted by trebuchet03
Another downside to the cast aluminum pan.... Steel drain bolt plugs on threaded aluminum... Stupid stupid stupid. Future designers and engineers, never do that - unless it's designed to come off very infrequently. If it must be aluminum, use an insert (helicoil, for example). Steel on Steel for fasteners that need to come off more than a few times.
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As an engineer I can appreciate your frustration, but honestly automobiles and many consumer devices aren't designed for metastable indefinite use. Having worked extensively with aluminum on (non-roadgoing) vehicles using steel bolts in contact with the aluminum is acceptable provided the bolts have *VERY* nice anti-corrosion coatings. Automotive manufacturers have pushed the envelope designing these and GM/Ford/Chrysler all have specifications of organic/teflon coatings that exceed 900 hrs B117 salt spray. They will last in aluminum for a very long time even in the presence of water and road salt. I believe most drain plug bolts for automobiles have an autophoretic paint (same as used on half shafts) that IIRC has a B117 salt spray rating between 1400-2000 hrs.
In the inevitable presence of oil as one would have with a drain plug galvanic corrosion will not be a concern within double the design life of the vehicle. Future designers and engineers should be aware that it's not ideal and there are risks, but the value of the benefits vs. the costs needs to be considered.