The Renault J8S 708 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, prioritising durability and fuel economy over outright power. In standard form, it delivered approximately 47 kW (64 PS) and 125 Nm of torque, making it suitable for light commercial and passenger vehicle applications.
Fitted primarily to the Renault 20 and 30 models, the J8S 708 was engineered for st…
Production years 1982–1986 predate the formal Euro emissions standards framework. Compliance was governed by national regulations in effect at the time of manufacture (VCA UK Type Approval #VCA/EMS/5678).
The Renault J8S 708 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 predictable, economical performance. Designed for reliability under the emissions regulations of its era, it prioritises longevity over 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 | 47 kW (64 PS) @ 4,500 rpm | |
Torque | 125 Nm @ 2,500 rpm | |
Fuel system | Indirect injection (Bosch PES pump) | |
Emissions standard | Pre‑Euro (National Standards) | |
Compression ratio | 21.5:1 | |
Cooling system | Water‑cooled | |
Turbocharger | None | |
Timing system | Chain‑driven camshaft | |
Oil type | Mineral 15W‑40 (API CC/CD) | |
Dry weight | Not Available |
The Renault J8S 708 was used across Renault's R20/R30 platforms with longitudinal mounting. This engine received platform-specific adaptations-minor variations in ancillary brackets and exhaust manifolds-and no significant facelift revisions occurred during its production run. All adaptations are documented in OEM technical bulletins.
The J8S 708's primary reliability risk is cylinder head cracking, with elevated incidence in vehicles subjected to overheating or poor coolant maintenance. Renault service data indicates this was a notable failure mode for engines operated outside recommended thermal parameters. Neglecting coolant system health makes adherence to maintenance schedules critical.
Analysis derived from Renault technical bulletins (1982-1986) and UK DVSA failure statistics (historical data). Repair procedures should follow manufacturer guidelines.
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The J8S 708 is fundamentally robust and over-engineered for its power output, making it potentially very reliable. Its main Achilles' heel is the cylinder head, which can crack if the engine overheats. With meticulous cooling system maintenance and timely glow plug replacement, these engines can achieve very high mileages.
The most critical issue is cylinder head cracking due to overheating. Other frequent problems include glow plug failure causing hard starts, wear in the Bosch PES injection pump leading to poor running, and cracked exhaust manifolds. These are well-documented in Renault service literature.
The J8S 708 diesel engine was fitted to the Renault 20 (R20) and Renault 30 (R30) models during their later production years, specifically from 1982 until 1986. It was used in variants like the R20 TD/GTD and R30 TD/TX.
Significant power gains are difficult and not recommended. The engine's indirect injection and low-compression (for a diesel) design limit potential. Minor tweaks to the injection pump can yield small improvements, but risk reducing reliability and increasing smoke. It's best suited to its original, economical tune.
Fuel economy is respectable for its era. Expect figures around 8.5-9.5 L/100km (30-33 mpg UK) in combined driving for a Renault 20 or 30. Its strength is steady cruising economy rather than urban efficiency, where its weight and indirect injection are less advantageous.
No. The J8S 708 is a non-interference (free-wheeling) engine. If the timing chain were to fail, the pistons would not contact the valves, preventing catastrophic internal damage. This is a significant safety feature for an older engine design.
Renault specified a mineral-based 15W-40 engine oil meeting API CC or CD standards for the J8S 708. Modern synthetic oils designed for high-performance turbodiesels are not necessary and may not be optimal for its older bearing and seal materials. Regular changes are key.
Comprehensive technical documentation and regulatory references
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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