PCV hose returns to the inlet of the turbo into an orifice that sees what is similar to a venturi type of vacuum. Crankcase at about 1000 foot altitude should show about 19"/Hg of vacuum at engine idle speeds. Can be measured at the dipstick tube with a cone type fitting to a vacuum gauge.
So if there is any pressure, would be negative.
Feel the major reason for camshaft cover failure is because its made out of plastic, do have thermoplastics that can easily handle 750*F, doubt if it is made out of these.
Another problem is using materials with different coefficients of expansion in an engine, an aluminum head has seven times the expansion of a cast iron block, never was a problem with heads when they were made of cast iron, sure is now. Good question what the thermo expansion of the plastic camshaft cover is on aluminum, mine had a crack in it. Another enemy is thermocycling, engines driven in the city for short trips have a lot more problems than engines running at long constant temperatures on the highway.
For years, O'rings were never used in engines or in AC systems, are now, another new problem that was never a problem before.
DIPSTICK SEAL
Part Number : 55594385
$3.63 Our Price $2.34
1982 GM 454 CID engine dipstick just has an unsealed metal cup welded to it. Suspect new EPA regulations want the crankcase to be at a high vacuum. Its PCV valve just plugs into a grommet on a stamped steel valve cover, with a short hose directly into the air cleaner, even at todays prices, extremely inexpensive to replace. 04 Cavalier was the same way, get ready to be robbed with the Cruze.
