Quote:
Originally Posted by SBSerpent
More thoughts on this topic. Steel backing plate on an aluminum water pump body. The CTE mismatch between dissimilar metals at high temperatures will create stress points where these two metals interact, which is at the gasket and the bolts between backing plate and water pump. Aluminum will expand and contract twice as much as steel for every degree of temperature change outside of room temperature. So I'm wondering whether this phenomenon is causing leaks at the gasket between the backing plate and the water pump.
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1) yes, but aluminum heads are bolted to cast iron blocks. The coefficient of expansion is in inches of expansion per inch of length. A head is 4 or 5 times longer so it would grow 4 or 5 times as much. In short, a very short length of two metals is not much differential expansion.
2) Alloys of metals or specific types of metal can have huge differences in their thermal coefficient of expansion, within a type of metal. I do know from the design of trade secret part, that I legally cannot divulge, there is a specific aluminum and a specific stainless steel that has very similar coefficients of thermal expansion. Hopefully the engineers who design this stuff know some things.