As far as the "milkshake" you refer to, it's not always the case with a blown head gasket. I think I was running with one for awhile...I would hear a high pitched hiss or squeal when I shut the motor off, I'm guessing this was pressure loss from the combustion chamber. Truck ran fine, for the most part, until one day it had a catastrophic meltdown. Started sounding like a diesel tractor and had no power at all. No water in the oil, and no oil in the radiator. Pulled her apart, had a massive gap in the head gasket between cylinders 2 and 3, luckily not between a cylinder and a water jacket (at least helped save my bearings) but cracked the head in both cylinders.

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1997 Ford Ranger XLT short bed regular cab
2.3L Lima
5 speed manual