source: 1966 122S owners manual
Diagrams of PCV
The PCV system has been source of some confusion because you will notice that between the B18 and B20 diagrams, the direction of flow at oil filler cap changes! The direction is not critical, in either case, the important thing for a properly working PCV system is a filtered fresh air source to mix with crankcase gases, and a path to the intake manifold to extract the mixed gases for burning. Problems occur typically when the extraction path is blocked (fouled PCV valve [No.4 on B18] or flame guard or nipple [B20]), this leads to crankcase pressurization and oil leakage around filler cap or other points of easy exit.
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B18 PCV
source: 1966 122S owners manual
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B20 (carbureted) PCV
source: 120 Series Intereurope workshop manual
162
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B20 (fuel injected) PCV
source: 1971 1800E Service Manual
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Link to interesting Brickboard thread: http://www.brickboard.com/RWD/index.htm?id=920391
Link to related thread for replacing the fresh air hook-up from front filter with a mini air filter mounted on the oil filler cap : http://www.brickboard.com/RWD/index.htm?id=1184285 ..this prevent condensate and/or oil in the front filter!