Quote:
Originally Posted by ds190
My tiny brain does not understand. If warming metal expands it, then wouldn't that increase the friction between the metals (either aluminum or iron or both), and make it more difficult to remove the glowplug? I would think it a glowplig would come out the easiest after the car was left outside overnight in 30 degree temps.
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Yes, but what is expanding exactly? The hole gets larger as the metal expands. The plug doesn't get wider, it may get a micron longer, but not wider.
Think of furniture. When wooden furniture dries out it shrinks. If you have a peg in a hole when the furniture is damp, and then you let it dry out, does the peg get loose, or does it get tight? It gets tight as the hole shrinks.