The Volkswagen AJ is a 1,588 cc, air‑cooled flat‑four petrol engine produced between 1973 and 1983. It features a single overhead camshaft (SOHC) per cylinder bank and a twin‑choke downdraft carburettor. This iteration, often called the "Type 4" engine, offered increased displacement and torque over its predecessors, providing more relaxed highway cruising.
Fitted primarily to the Volkswagen Type 4 (411/412) and later the Volkswagen Bus (T2 Bay Window, 1972-1979), the AJ engine was engineered for durability and ease of maintenance in varied global markets. Emissions compliance for its era was managed through basic carburettor jetting and ignition timing, meeting the prevailing standards prior to widespread catalytic converter adoption.
One documented service concern is oil cooler seal failure, which can lead to external leaks and reduced cooling efficiency. This issue, referenced in Volkswagen Service Technical Bulletin No. 1‑74‑03, is often linked to thermal cycling and seal material degradation over time. Production concluded in 1983 with the end of the Type 4 platform, succeeded by water‑cooled engine designs.
Volkswagen
Production years 1973–1983 predate formal Euro emissions standards. Compliance was governed by national regulations of the time (e.g., US EPA standards for North American models).
The Volkswagen AJ is a 1,588 cc air-cooled flat-four engineered for passenger cars and light commercial vehicles (1973-1983). It combines a robust cast-iron crankcase with a twin-choke carburettor to deliver smooth, low-RPM torque and mechanical simplicity. Designed for global markets, it balances reliability with serviceability, predating modern emissions mandates.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,588 cc | |
| Fuel type | Petrol | |
| Configuration | Flat-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 94.0 mm × 57.0 mm | |
| Power output | 52–55 kW (70–75 PS) | |
| Torque | 123–128 Nm @ 3,000 rpm | |
| Fuel system | Twin-choke downdraft carburettor (Solex 34 PICT-3) | |
| Emissions standard | Pre-Euro (National standards apply) | |
| Compression ratio | 7.5:1 | |
| Cooling system | Air-cooled (fan-forced) | |
| Turbocharger | None | |
| Timing system | Gear-driven camshafts | |
| Oil type | SAE 20W-50 (Mineral) | |
| Dry weight | 100 kg |
The air-cooled design provides mechanical simplicity but requires vigilant monitoring of oil temperature and fan belt condition, especially under load or in hot climates. SAE 20W-50 mineral oil is critical for its high-temperature stability and compatibility with older seals. The gear-driven timing system is highly durable but necessitates precise valve lash adjustment every 10,000 km. The Solex carburettor demands periodic synchronization and jet cleaning to maintain optimal mixture. Oil cooler seals (ref. VW SIB 1-74-03) are a known wear item and should be inspected during major services.
Oil Specs: Requires SAE 20W-50 mineral oil (Volkswagen Owner's Manual, 1974). Modern synthetics may not be suitable for all seals.
Emissions: Pre-dates Euro standards. Compliance was with national regulations (e.g., US EPA) of the production era.
Power Ratings: Measured under DIN 70020 standards. Output varies slightly by model year and market (Volkswagen Historical Archive).
Volkswagen Workshop Manual (Type 4)
Volkswagen Owner's Manual (Type 4, 1974)
Volkswagen ETKA Parts Catalogue
Volkswagen Service Technical Bulletin No. 1-74-03
The Volkswagen AJ was used across Volkswagen's Type 4 platform with rear, longitudinal mounting. This engine received platform-specific adaptations-slight variations in intake manifolds and engine tinware for the Bus (T2) versus the 411/412-creating minor parts differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the crankcase, typically on the generator/alternator stand boss or near the oil filler (Volkswagen Workshop Manual). The AJ code is usually accompanied by a sequential serial number. Visual identification: Air-cooled flat-four with prominent cooling fan housing on top and a single carburettor on the driver's side. Critical differentiation from earlier Type 1 (Beetle) engines: AJ is physically larger, uses a 5-bolt flywheel/clutch, and has a different oil cooler mounting configuration. Service parts are generally specific to the AJ and not interchangeable with smaller Type 1 engines.
The AJ's primary reliability consideration is oil cooler seal failure, with elevated incidence in high-mileage or thermally-stressed engines. While not catastrophic, leaks can lead to low oil levels and overheating. Regular inspection and using correct oil viscosity make preventative maintenance critical.
Analysis derived from Volkswagen technical bulletins (1970-1985) and owner club technical archives (1970-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VOLKSWAGEN AJ.
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Regulation (EC) No 715/2007
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