The Volkswagen AP is a 1,588 cc, air‑cooled flat‑four petrol engine produced between 1973 and 1983. It featured a single overhead camshaft (SOHC) per cylinder bank and a twin‑choke downdraft carburettor, delivering outputs ranging from 44 kW (60 PS) to 55 kW (75 PS) with torque figures around 108–122 Nm. Its air‑cooled design simplified maintenance in varied climates but required vigilant cooling system checks.
Fitted primarily to the Type 4 (411/412) and early Type 2 (T2 Bay Window) models, the AP engine was engineered for dependable, economical transportation with a focus on low‑end torque for load carrying. Emissions compliance for its era was managed through carburettor jetting and ignition timing, meeting the applicable national standards of the time prior to widespread Euro regulations.
One documented concern is oil cooler seal failure, which can lead to external leaks and potential oil starvation. This issue, referenced in Volkswagen Service Technical Bulletin 1‑76‑03, is often linked to seal degradation from age and heat cycling. Production ended in 1983 as Volkswagen transitioned fully to water‑cooled engines across its range.
Volkswagen
Production years 1973–1983 predate formal Euro emissions standards. Compliance was based on national regulations in effect at time of manufacture (VCA UK Type Approval historical records).
The Volkswagen AP 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 single overhead camshaft design to deliver smooth, low-RPM torque and mechanical simplicity. Designed for the regulatory environment of its era, it prioritises durability over modern emissions controls.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,588 cc | |
| Fuel type | Petrol | |
| Configuration | Flat-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 85.5 mm × 69.0 mm | |
| Power output | 44–55 kW (60–75 PS) | |
| Torque | 108–122 Nm @ 2,800–3,500 rpm | |
| Fuel system | Solex 34 PICT-3 twin-choke carburettor | |
| Emissions standard | Pre-Euro (National Standards) | |
| Compression ratio | 7.5:1 – 8.2:1 | |
| Cooling system | Air-cooled (fan-forced) | |
| Turbocharger | None | |
| Timing system | Gear-driven camshafts | |
| Oil type | SAE 15W-40 (Mineral) | |
| Dry weight | 100 kg |
The flat-four layout provides a low center of gravity and smooth operation but requires diligent inspection of the external oil cooler and its seals to prevent leaks. SAE 15W-40 mineral oil is specified for its compatibility with older seal materials and the air-cooling system's thermal profile. The Solex carburettor needs periodic synchronization and jet cleaning to maintain fuel economy and prevent hesitation. Valve clearances must be manually adjusted every 10,000 km as per the workshop manual. Oil cooler seal replacement is a common preventative maintenance task per SIB 1-76-03.
Oil Specs: Requires SAE 15W-40 mineral oil specification (Volkswagen SIB 1-76-03). Modern synthetic oils may not be suitable for original seals.
Emissions: Pre-dates formal Euro standards. Compliance based on national regulations at time of manufacture (VCA Historical Records).
Power Ratings: Measured under DIN 70020 standards. Output varies by compression ratio and carburettor setup (Volkswagen Workshop Manual M-01-73).
Volkswagen Technical Information System (TIS): Workshop Manual M-01-73
Volkswagen ETKA Parts Catalogue: Docs 001-1588
Volkswagen Service Information Bulletin (SIB): 1-76-03
UK Vehicle Certification Agency (VCA) Historical Type Approval Database
The Volkswagen AP was used across Volkswagen's Type 4 platform with rear-engine, rear-wheel-drive layout. This engine received platform-specific adaptations-unique engine mounts and cooling shrouds for the 411/412 saloon and the Type 2 (T2) van-and from 1976 minor carburettor and ignition updates were implemented for emissions, creating minor parts variations. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the crankcase, just below the generator/alternator stand (Volkswagen TIS M-01-73). The code "AP" is typically followed by a serial number. Visually, it is identifiable as an air-cooled flat-four with a prominent external oil cooler mounted on the front of the fan housing. Critical differentiation from earlier Type 1 (Beetle) engines: The AP (Type 4) engine has a wider, more robust crankcase with integrated oil pump and different cooling tin configuration. Service parts for the AP are distinct from Type 1 engines; mixing components is not advised.
The AP's primary reliability risk is oil cooler seal failure, with elevated incidence in high-mileage or neglected examples. Volkswagen service data from the late 1970s indicated this was a frequent cause of oil leaks, while owner club surveys consistently rank cooling system integrity as a top maintenance item. Infrequent oil changes and overheating cycles accelerate seal degradation, making proactive inspection critical.
Analysis derived from Volkswagen technical bulletins (1973-1983) and owner club technical archives (1975-2023). Repair procedures should follow manufacturer guidelines.
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VOLKSWAGEN Official Site
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EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
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DVLA: Engine Changes & MoT
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Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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VCA Certification Portal
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