The Volvo B 6304 S is a 2,922 cc, inline‑six petrol engine produced between 1991 and 1998. It features a dual overhead camshaft (DOHC) design with 24 valves and multi‑point fuel injection. This naturally aspirated powerplant delivered outputs ranging from 170 to 204 PS, providing smooth, linear power delivery characteristic of Volvo's engineering philosophy.
Fitted primarily to the 960 sedan and wagon (including the 964 and 965 variants), the B 6304 S was engineered for refined, quiet operation and long‑distance cruising comfort. Emissions compliance for its era was managed through electronic fuel injection and catalytic converters, meeting the prevailing Euro 1 and early Euro 2 standards depending on the model year and market.
One documented service concern involves the electronic throttle module (ETM), which can develop erratic idle or hesitation issues due to internal carbon buildup or potentiometer wear. This is addressed in Volvo Technical Service Bulletin TSB‑001‑1997, which details inspection and replacement procedures for affected units.
Production years 1991–1995 meet Euro 1 standards; 1996–1998 models meet Euro 2 compliance depending on market (VCA UK Type Approval #VCA/EMS/VOLVO960).
The Volvo B 6304 S is a 2,922 cc inline‑six naturally aspirated petrol engine engineered for executive sedans and wagons (1991-1998). It combines DOHC 24-valve architecture with multi-point fuel injection to deliver smooth, linear power and quiet refinement. Designed to meet Euro 1 and Euro 2 standards, it prioritizes drivability and durability over outright performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,922 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑6, DOHC, 24‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 81.0 mm × 90.0 mm | |
| Power output | 170–204 PS (125–150 kW) | |
| Torque | 260–280 Nm @ 4,000–4,700 rpm | |
| Fuel system | Bosch LH 2.4 or 3.2 multi-point injection | |
| Emissions standard | Euro 1 (pre-1996); Euro 2 (1996-1998) | |
| Compression ratio | 10.3:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven | |
| Oil type | SAE 10W-30 or 5W-30 (ACEA A3/B3) | |
| Dry weight | 190 kg |
The inline-six configuration provides inherent smoothness and a broad torque curve, ideal for relaxed cruising but less suited to aggressive acceleration. Regular replacement of the timing chain tensioner (recommended every 150,000 km) is critical to prevent chain slap and potential guide damage. The Bosch LH injection system is generally robust but sensitive to fuel quality; using high-octane, low-ethanol fuel is advised. The electronic throttle module (ETM) is a known wear item; symptoms like rough idle warrant immediate inspection per TSB-001-1997. Coolant should be changed every 5 years to protect the aluminum head and cast-iron block.
Oil Specs: Requires ACEA A3/B3 specification oil (Volvo Owner's Manual 960). Viscosity may vary by climate (10W-30 for warmer regions).
Emissions: Euro 1 certification applies to 1991-1995 models (VCA Type Approval #VCA/EMS/VOLVO960). Euro 2 compliance is for 1996-1998 models.
Power Ratings: Measured under DIN 70020 standards. Higher 204 PS output found in later 965 models (Volvo Group PT-1998).
Volvo Technical Service Manual (TP 30760)
Volvo Electronic Parts Catalogue (EPC): Doc. VEP-960-01
VCA Type Approval Database (VCA/EMS/VOLVO960)
The Volvo B 6304 S was used exclusively across Volvo's 960 platform with longitudinal mounting. This engine received minor ECU and emissions revisions for the 1995 model year facelift, creating slight interchange limits for electronic components. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on a flat boss on the left side of the cylinder block, near the rear of the engine (Volvo TP 30760). The 8th digit of the VIN is 'B' for 960 models with this engine family. Pre-facelift (1991-1994) engines typically have a silver cam cover with "24V" embossed; facelift models (1995-1998) often have a black cam cover. Critical differentiation from the B6254: The B6304S has a 3.0L displacement (bore 81mm) versus the 2.5L (bore 83mm) of the B6254. ECU part numbers differ significantly between pre- and post-facelift models; ensure compatibility when sourcing replacements.
The B 6304 S's primary reliability risk is electronic throttle module (ETM) failure, with elevated incidence in high-mileage vehicles. Volvo TSB TSB-001-1997 documents this as a prevalent service issue, while general owner reports frequently cite cooling system component wear after 200,000 km. Infrequent oil changes can accelerate timing chain tensioner wear, making adherence to service intervals critical.
Analysis derived from Volvo technical bulletins (1995-1998) and aggregated owner-reported failure data (1998-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about VOLVO B-6304-S.
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DVLA: Engine Changes & MoT
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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