The Renault J8S 738 is a 2,068 cc, inline‑four naturally aspirated diesel engine produced between 1982 and 1986. It features a SOHC, 8‑valve design with indirect injection via a Bosch mechanical fuel pump. This robust and simple engine prioritized durability and fuel economy over high performance, making it suitable for commercial and passenger vehicles of its era.
Fitted primarily to the Renault 20 and 30 (R20/R30 TD), the J8S 738 was engineered for steady, reliable transportation and moderate load carrying. Its driving character is defined by low-revving torque and mechanical simplicity. Emissions compliance for its production period was met through basic engine design, predating stringent Euro standards.
One documented concern is cylinder head cracking, particularly between valve seats, which can lead to coolant loss and combustion issues. This potential failure mode, referenced in Renault internal service documentation, is often attributed to thermal stress from overheating or localized hot spots in the head casting.
Production years 1982–1986 predate formal Euro emissions standards (EU Directive 88/77/EEC).
The Renault J8S 738 is a 2,068 cc inline‑four naturally aspirated diesel engineered for mid‑size sedans and estates (1982-1986). It combines indirect injection with a simple SOHC valvetrain to deliver dependable low-end torque and mechanical longevity. Designed for an era before formal Euro standards, it prioritizes robustness and economy over emissions or high output.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,068 cc | |
| Fuel type | Diesel | |
| Configuration | Inline‑4, SOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 88.0 mm × 85.0 mm | |
| Power output | 51 kW (69 PS) | |
| Torque | 132 Nm @ 2,500 rpm | |
| Fuel system | Bosch mechanical injection pump | |
| Emissions standard | Pre-Euro (No formal standard) | |
| Compression ratio | 22.5:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven | |
| Oil type | Mineral 15W‑40 (API CC/CD) | |
| Dry weight | Not specified in available OEM docs |
The high compression ratio provides strong low-RPM torque ideal for steady cruising but requires strict adherence to cooling system maintenance to prevent cylinder head cracking. Mineral 15W-40 oil meeting API CC/CD specifications is critical for protecting the older engine design and mechanical injection pump. Regular valve clearance checks are essential due to the mechanical lifters. The Bosch injection pump demands clean, water-free diesel to prevent internal seizure. Cylinder head integrity should be monitored, especially if the engine has a history of overheating.
Oil Specs: Requires mineral 15W-40 meeting API CC/CD specifications (Renault Workshop Manual 820). Modern low-ash oils are not recommended.
Emissions: Formal Euro emissions standards did not apply during production (1982-1986). Compliance governed by national regulations preceding EU Directive 88/77/EEC.
Power Ratings: Measured under EEC 80/1269 standards. Output is consistent across model years (Renault Group PT-1985).
Renault Technical Information System: Workshop Manual 820, Technical Bulletin J8S-01
EU Legislation: Directive 80/1269/EEC (Power Measurement), Directive 88/77/EEC (Emissions)
Renault Group Parts & Technical Catalogue (PT-1985)
The Renault J8S 738 was used across Renault's R20/R30 platforms with longitudinal mounting. This engine received minimal platform-specific adaptations beyond ancillary bracketry. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the flat machined surface on the left side of the engine block, near the injection pump (Renault Workshop Manual 820). The code will read "J8S 738". Visually, it is identifiable by its cast iron block, aluminum cylinder head, and prominent Bosch mechanical injection pump mounted on the right side. Differentiation from the similar J8S 736 (used in R21) is primarily by application and minor ancillary differences; the core engine is identical. Service parts for the J8S family are generally interchangeable.
The J8S 738's primary reliability risk is cylinder head cracking, with elevated incidence following overheating events. While robust overall, Renault internal data noted this as a recurring failure point in high-mileage or poorly maintained engines. Ensuring a perfectly functioning cooling system and avoiding aggressive driving when cold make preventative maintenance critical.
Analysis derived from Renault technical bulletins (1982-1986) and internal service documentation. Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about RENAULT J8S-738.
Comprehensive technical documentation and regulatory references
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RENAULT 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
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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
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VCA Certification Portal
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