Is Your Engine Breathing Properly?
Have you noticed oil on the top or your engine and don’t know where it’s coming from? Have you checked your filler cap and found the filter material in the cap full of oil? Marvin Pickens and I had this problem. All engines develop crankcase pressure which gets worse as the engine and rings get older. Crankcase pressure needs to be ventilated, and there may be a problem with the breather filter located on the underside of the lifter cover. The Buick Shop Manual states this about ENGINE CRANKCASE VENTILATION:
“Crankcase ventilation is provided by the ventilating type oil filler cap located at the front end of the valve lifter cover and the crankcase ventilator pipe connected to the rear end of the lifter cover. The filler cap contains a gauze filtering element to exclude dirt. A gauze filled breather filter is built into the rear end of the lifter cover to remove oil from the air stream before it leaves the crankcase.
The ventilator pipe extends down to near the bottom of the engine so that air passing the open end will create suction when the car is moving forward. The middle transverse web of the crankcase and a baffle mounted above it form a partition which causes the draft of air to be drawn downward through the front section of the crankcase and upward through the rear section. As the air stream reverses direction in the filter, oil is separated and drained back through a hole in the rear end of the filter. “
Below you can see the shop manual air flow diagram and the underside of Marvin’s lifter cover. Marvin cut open the filter and found it totally clogged with dried oil. When this filter gets clogged air will not flow out the rear ventilator pipe and crankcase pressure will push oil out through the oil filler cap, depositing oil on the lifter cover which gets blown onto the engine and engine compartment. The only way to clean this enclosed welded breather filter element is to boil the lifter cover in a degreaser bath, or cut it open to replace and re-weld it as Marvin has. GM realized this system was inefficient and in later years provided valve covers with breathers, and then a PCV valve system. It is important to also keep the element in your filler cap clean. If you drive your Skylark a lot you may consider changing your valve covers to aftermarket covers with breathers.