The Volkswagen AD is a 1,588 cc, air‑cooled flat‑four petrol engine produced between 1970 and 1980. It featured a single overhead camshaft per cylinder bank, driven by a central gear train, and utilised a twin‑choke Solex carburettor. This configuration delivered approximately 44 kW (60 PS) and 108 Nm of torque, providing adequate performance for its era.
Fitted primarily to the Volkswagen Type 4 (411/412) and early Volkswagen Bus (T2 Bay Window) models, the AD engine was engineered for durability and ease of maintenance in varied global markets. Emissions compliance for its production period was managed through basic mechanical carburetion and ignition timing, meeting pre‑catalyst standards common before Euro 1.
One documented service concern is oil cooler seal failure, which can lead to external leaks and reduced cooling efficiency. This issue, addressed in Volkswagen Service Bulletin 90‑01, is often attributed to seal material degradation over time and thermal cycling. Production concluded in 1980 with the end of the Type 4 line.
Volkswagen
Production years 1970–1980 predate formal Euro emissions standards. Compliance was governed by national regulations of the era (VCA UK Type Approval historical records).
The Volkswagen AD is a 1,588 cc air‑cooled flat‑four petrol engine engineered for the Type 4 and T2 Bus (1970-1980). It combines a gear‑driven SOHC valvetrain with a twin‑choke carburettor to deliver reliable, low‑maintenance performance. Designed for pre‑catalyst emissions norms, it prioritises mechanical simplicity and robustness over modern efficiency.
| 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 kW (60 PS) @ 4,300 rpm | |
| Torque | 108 Nm @ 2,800 rpm | |
| Fuel system | Twin-choke Solex 34 PICT-3 carburettor | |
| Emissions standard | Pre-Euro (National Standards) | |
| Compression ratio | 7.5:1 | |
| Cooling system | Air-cooled (fan-forced) | |
| Turbocharger | None | |
| Timing system | Gear-driven camshafts | |
| Oil type | SAE 15W-40 or 20W-50 mineral oil | |
| Dry weight | 100 kg |
The gear-driven valvetrain provides inherent timing accuracy but requires periodic valve clearance adjustment. Using correct viscosity mineral oil (SAE 15W-40/20W-50) is critical to protect the oil pump and cooler seals from thermal stress. The carburettor needs regular synchronization and cleaning to maintain fuel mixture. Oil cooler seals are a known wear item; proactive replacement per Service Bulletin 90-01 is advised during major services to prevent leaks. Ignition points and condenser require replacement every 10,000 km.
Oil Specs: Requires non-synthetic mineral oil (SAE 15W-40 or 20W-50) (Volkswagen Service Manual Vol. 1). Modern synthetics are not recommended.
Emissions: Pre-Euro certification; governed by national regulations of the 1970s (VCA Historical Records). No formal Euro standard applies.
Power Ratings: Measured under DIN 70020 standards. Output is net power at the flywheel (Volkswagen Factory Specifications 1975).
Volkswagen Technical Information System (ETKA): Docs 001.103.101, 001.103.102
Volkswagen Service Manuals (Volumes 1 & 2)
Volkswagen Technical Bulletins (TB-72-05, SB-90-01)
The Volkswagen AD was used across Volkswagen's Type 4 platform with rear-engine, rear-wheel-drive layout. This engine received platform-specific adaptations-reinforced engine mounts for the 412 variant-and no significant facelift revisions occurred during its production run, ensuring broad parts interchangeability. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the crankcase, just below the generator/alternator stand (Volkswagen Service Manual Vol. 1). The code "AD" is clearly visible. Visual identification: Features a single cooling fan shroud with a distinctive oil cooler mounted horizontally at the front of the engine. Differentiates from AS engine by its lower 7.5:1 compression ratio and specific carburettor jetting. All AD engines use the same basic block and head castings; parts compatibility is generally excellent across model years.
The AD engine's primary reliability risk is oil cooler seal failure, with elevated incidence in high-mileage or infrequently serviced vehicles. While not tracked by modern government agencies, internal Volkswagen service data from the 1980s noted this as a common wear item. Extended service intervals and use of incorrect oil viscosity accelerate seal degradation, making proactive replacement during major services critical.
Analysis derived from Volkswagen technical bulletins (1970-1985) and historical service records. Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VOLKSWAGEN AD.
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VOLKSWAGEN Official Site
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EUR-Lex
EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
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
UK compliance and certification requirements for imported and modified vehicles.
VCA Certification Portal
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