Loss of coolant but no apparent leak, milk shake looking motor oil (coolant in oil), coolant in radiator oily looking, white smoke out tail pipe and over heating. Just to name a few. Can have just one of these or all at same time.
Additionally, the engine could have a "skip" to it. Run ruff. Shake on acceleration. With a blown head gasket the engine will be running on one or more less cylinders.
Let's not forget the horrible pre-ignition pigging if it's blown between cylinders.
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