I Love reading this thread because aside from learning a lot, I also got entertained from all of the stories you share.
Recently I bought a used Pajero with a 4D56T engine which according tot he previous owner was blowing bubbles in the radiator since he could remember.
Me being a guy who hates malfunctioning engines, I decided to remove the cylinder head to replace the head gasket.
During removal of the cylinder head bolts I discovered that some of the bolt have different torques among the rest, and eventually 3 bolts around cylinder #1 are stuck and cannot be loosened normally. That little head gasket replacement exploded in to a more worn out head and cracked parts along the way.
The gasket in cylinder #1 was blown and was leaking combustion gasses in to the nearest water port and also into the 3 cylinder head bolts which was stubborn to loosen that after years of use has almost glued itself into the engine block.
Also found that the crankshaft pulley bolt was way too loose for its required torque.
Eventually after 3 weeks of of every weekend from work that I was spending my time rebuilding the cylinder head, I was able to put everything back.
And voila!
A few bursts of 3second cranks while pumping the primer pump the engine turned over and it was WAY quieter than it previoulsy ran...
I just couldnt fathom how can some mechanics will do a job and say "ok thats fine already its running" without making sure that the engine was done properly...