Having read the other posts up to this time, there is but little to add.

The small hose from the flame trap to the intake manifold is vital to reducing crankcase pressure when the engine is at idle. The brass nipple into the intake manifold is a common culprit. Can clog with hardened stuff. Take the fitting off (keep bits of the stuff out of the manifold) and use a 3/32-inch drill bit to clean and clear the passageway. Put on a new hose, too.

The two downward routes from the oil separator box into the crankcase are for (1) oily vapors to come upward, and (2) separated out oil droplets to go back down. It is the upward one that must be clear. If the crankcase becomes overfilled (very rare, but...) and the bottom end of that upflow tube is covered, the pressure will have no relief.

Pressure in the crankcase can find release through any weak seal. The usual seals are Front main seal, rear main seal, camshaft seal and intermediate shaft seal.

Oil pan gasket leakage is rare. Rear main seal is common. Than one drips out at the rear of the block, shows up on the ground like a tranny leak would.

Leaks often seem to heal themselves once the PCV system is working well. Seals don't do that unless they are Navy Seals or fur-bearing animals.

Next time you are in for timing belt replacement, check the three seals on the front of the block. They are easy replacements, unlike the rear main seal which requires that the tranny be pulled.

Good Luck,

Bob

:>)