Well thats good news. I was just thinking about the horrors of the last time I had "Jiffy Lube" service one of my vechicles. To make a long story short, it ended up costing me $4,600.00 in attorney fees and I still had a blown motor.
Very light mechanical guy I must say. There cannot be a seal with an untapered thread and no sealing implement. Furthermore, the plug is steel; the casing is aluminum. When heated, the aluminum expands twice as much as the steel so the gap where thread meets thread increases (ie the diameter of the threaded hole grows more than the plug). Aluminum expands about twice the amount that carbon steel does on a per Fahrenheit degree basis. The thread fit has to loosen when engine heats. With a gasket, the sealing actually gets tighter as the engine heats. The aluminun housing is hotter than the steel plug because the aluminum is a better conductor. Heat moves from the oil to the aluminum and steel. It is then lost to the atmosphere. Because the aluminum is a far better conductor than carbon steel, the temperature of the aluminum will be higher than that of the steel. So the aluminum thickens a little more than the bolt grows due to the difference in thermal expansion. That is why the gasket gets squeezed more when engine is hot. Time to get off the soapbox.
Well that's the rub...the bolt is steel and the housing is aluminum. I don't know how often it happens, but someone posted of having the threads come out with the bolt...
Can someone discuss the metallurgical principle behind the "annealing" of the copper washer by heating "red hot" and then letting it cool? Is the original copper lattice (3-3-1 or such) disrupted by the prior use and are we correcting this? What is wrong with the original washer that this process fixes? Thanks. Jim S.
Copper and some other metals "work harden', that is any mechanical deformation will cause the material to become harder or stronger to some extent. The heating and slow cooling (annealing) will undo this effect, however too many cycles of this will cause increased grain size growth which is an undesirable side effect.
