Hot air should NOT blow out of the dipstick tubing while the motor is running.
The PCV valve is a one way passage that allows the gases caused by blow-by (piston rings/valve stems) to escape into the open air/inlet manifold), to avoid pressure to build up in the crankcase. The engine in question has positive pressure in the crankcase, the important question is why. Most likely a defective PCV-valve clogged by sludge since I doubt that such a valve suffers from mechanical breakdown very often since it's most likely just a spring loaded steel ball inside a piece of tubing. Furthermore,-why is the PCV-valve clogged up?
Worn piston rings? Worn valve stems? Both scenarios causes blow by.
If this motor has been running in this condition for a long time the oil will have been diluted by the unburned gases and also been subject to the build up of sludge and not to mention the risk of damaged oil seals.
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