Wolfsburg Wired, May, 2001

Bus Air Filter Versions

Late'49-Late'53, except Pickup and Ambulance This air cleaner is often referred to as the "coffee can" air cleaner. This style cleaner has 10 holes located on the left side, which allowed for an intake of air. The inner cylinder was packed with hair material, which was to be soaked in degreasing cleaning solvent, dried and moistened with SAE 20 engine oil. Mann was the manufacturer of this particular filter. Knecht made another style and was available as an option and intended for dusty regions. This air cleaner was cylindrical in design, and had 2 intake slots located in the housing. This air cleaner is comprised of two halves, which were held together by 2 spring clips. When separated, an internal filter could be easily cleaned, then reinstalled.


Late'53-Mid'55, except Pickup and Ambulance This was the start of the oil bath style air cleaner as standard equipment for VW. This particular cleaner was installed intermittently along with the "coffee can" style filter, starting in late 1953. This air cleaner featured an upper and lower hemisphere, with the upper hemisphere being secured to the lower by means of a metal strap. The lower chamber of the filter was to be filled to an inscribed mark with SAE 20 engine oil. The upper portion housed a fibrous material, which was to be soaked in degreasing solvent, dried, then moistened with SAE 20 engine oil. This was the first oil bathed filter that was available for VW's. The oil bathed filter functions by extracting dust and dirt by means of pulling heavy particles downward within the lower chamber, and trapping them within a pool of oil. The oil bathed filter also served as an air intake noise damper. The late'53 strap style air filters were made with one minor flaw (see lower photo) in that the upper portion lacked a lip, which allowed moisture to flow into the lower chamber. The 1954 design included this lip and thus cured the water infiltration dilemma. This air cleaner was used intermittently in 1953, thus there is no chassis number for its birth. However, it was used through Feb'55, ending with chassis number 20-117902

Mid'55-Mid'56 VW introduced an entirely new air cleaning arrangement. This air cleaner was mounted remotely by means of a metal duct. The air filter element portion is secured to the elbow of the duct with a wing nut, which is secured to the base of the filter element.

Mid'56 - May'59, 36 hp (Photo not available) The filter element is secured by means of a fixed stud, the wing nut was omitted.

May'59 - May'60, Bastard 40hp Clamps are added to hold the two halves of the filter element together.


May'60 - Sep'64(1965 model year), 40hp only VW introduced an entirely new air cleaning arrangement starting with the May'60 model year. It featured a warm air intake hose and a controllable flap valve. The controllable flap valve, in the released position at temperatures under 67 degrees Fahrenheit, is opened by means of an induction of air as the the engine speed increases. The valve shaft is equipped with a small weight for compensation purposes. In the fixed position, at temperatures of 68 degrees Fahrenheit and higher, the air intake tube is opened and the connection for the pre-heater pipe from the left heater junction box is closed by the valve simultaneously. Thus, this clever arrangement supplies warm air at low engine speeds in an effort to prevent the formation of ice inside the carburetor, particularly when the weather is cold, and also helps with fuel conservation.

1963 - Sep'63 with 1500cc option The duct is re-worked a bit with the inclusion of a rubber hose.

Oct'63-1967 The air cleaner assembly is now mounted on the right hand side of the fan housing.


1968-1970 Starting with this year the air intake flap regulates according to engine temperature. The cold engine draws air from the cylinder/head area where the engine warmth is created quickest. This flap is regulated via a cable that connects to the air flaps at the base of the fan shroud. Also incorporated was an additional flap that controlled the fumes entering from the crankcase. At higher speeds this flap is opened and fumes from the crankcase are drawn into the intake system. This is one example of many pollution controls that VW was implementing in 1968-1969. 1971 only Starting with engine AE 0 000 001 VW incorporated a separate thermostat located on the backside of the air filter assembly. Incorporating a separate thermostat deleted the cable that tethered the air filter assembly to the engine on prior models thus allowing for a much simpler/quicker cleansing.


1972 only The flap regulating intake air is now controlled by two factors, engine load and air temperature being drawn in. This new system responds quicker to engine operation conditions. Intake manifold vacuum is routed through a thermostat, mounted to the air intake of the air cleaner, into a vacuum servo mounted to the air intake snout. This servo actuates a flap that controls the intake of air flow, warm air from the head/cylinder area or cool air from the engine compartment.

1973-1974 and 1973-1979 engines without fuel injection VW moved from the oil bath filtration system to the newer paper element style. The housing is now constructed of plastic. Intake air regulation is controlled using the same methods described in the 1972 only above.