Blowby is an escape of combustion gasses past the rings on the pistons when the rings or cylinder walls are excessively worn, hence the name "blowby" (under the pressure generated by the fuel-air charge, some of the combustion gasses blow past the rings. This hot, nasty gas gets into the crankcase and can cause numerous different problems. To combat this evil force, automotive engineers designed a system called "positive crankcase ventilation" or as we know it "PCV". This system is designed to suck (so to speak) in a positive fashion, all of the evil gases floating around in the crankcase. BTW, these gasses can be very evil. Back in my racing days, we had built a 400 cubic inch Oldsmobile motor for 1380 racing. We were using alcohol for fuel. Well that baby broke a ring during a hard run and filled the crankcase full of alcohol/air combustion charge. When the mag thru a spark at that cylinder, the motor blew up like we had been feeding it c-4. Took out the sump, valve covers, valley cover, caught fire, etc., etc. I wasn't looking at the time, but they told me it made a pretty bluish orange cloud when it went off. So the PVC system makes a lot of sense for a lot of good reasons. Whew!!, too much typing in one day..

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Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.