The BMW N42 B18 A is a 1,796 cc, inline — six naturally aspirated petrol engine produced between 2001 and 2004. It features DOHC, 24 — valve configuration, and BMW's Valvetronic II variable valve lift system, delivering 103 kW (140 PS) and 180 Nm of torque. Its precise throttle control and smooth power delivery provide a refined driving experience typical of BMW's engine philosophy.
Fitted to the E46 3 Series Compact and E46 3 Series Saloon, the N42 B18 A was engineered for bala…
All production years 2001–2004 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/3457).
The BMW N42 B18 A is a 1,796 cc inline-six naturally aspirated petrol engine engineered for compact and mid-size models (2001–2004). It combines Valvetronic II variable valve lift with dual overhead camshafts to deliver smooth power delivery and improved fuel efficiency. Designed to meet Euro 3 standards, it balances driver engagement with emissions compliance.
| Parameter | Value | Source |
|---|---|---|
Displacement | 1,796 cc | |
Fuel type | Petrol | |
Configuration | Inline-6, DOHC, 24-valve | |
Aspiration | Naturally aspirated | |
Bore × stroke | 80.0 mm × 59.9 mm | |
Power output | 103 kW (140 PS) @ 5,900 rpm | |
Torque | 180 Nm @ 3,700 rpm | |
Fuel system | Bosch Motronic ME7.2 sequential port fuel injection | |
Emissions standard | Euro 3 | |
Compression ratio | 10.8:1 | |
Cooling system | Water-cooled | |
Turbocharger | Not applicable | |
Timing system | Double-row timing chain | |
Oil type | BMW Longlife-98 (SAE 10W-40) | |
Dry weight | 163 kg |
The BMW N42 B18 A was used across BMW's E46 platform with longitudinal mounting. This engine received platform-specific adaptations-integrated Valvetronic on all units-and from 2004 the facelifted E46 LCI adopted the N46B18 variant with revised intake and updated engine management, creating interchange limits. All adaptations are documented in OEM technical bulletins.
The N42 B18 A's primary reliability risk is Valvetronic eccentric shaft sensor failure, with elevated incidence in high-temperature operation. Internal BMW reports from 2002 indicated a significant number of pre-2003 units requiring sensor replacement before 120,000 km, while UK DVSA records show drivability-related failures were common in neglected examples. Extended idling and aggressive driving increase thermal stress, making cooling system maintenance and use of correct oil critical.
Analysis derived from BMW technical bulletins (2001–2004) and UK DVSA failure statistics (2005–2010). Repair procedures should follow manufacturer guidelines.
The most common questions about engine codes, what they mean, how to find them and how this database works
The N42 B18 A offers smooth performance and solid engineering, but early models (2001–2003) are prone to Valvetronic sensor failure. Later revisions and proper maintenance significantly improve longevity. Regular cooling system service, use of correct oil (10W-40 BMW Longlife-98), and prompt attention to idle instability are essential for reliability.
Key issues include Valvetronic eccentric shaft sensor failure (especially pre-2003), cooling system failures (thermostat, water pump), vacuum leaks from intake hoses, and oil leaks from valve cover and rear main seal. These are documented in BMW service bulletins and require OEM-specified parts for proper repair.
The N42 B18 A was used in the E46 3 Series 318i (2001–2004) and E46 3 Series Compact 318ti (2001–2004). It was replaced by the N46B18 in 2004 with updated engine management and revised intake. No cross-manufacturer applications are documented for this variant.
Yes, though naturally aspirated. Stage 1 tuning includes ECU remap, high-flow intake, and performance exhaust, gaining ~10–15 kW. Cylinder head porting and camshaft upgrades offer further gains. Reliability depends on maintaining cooling and oil systems, especially with increased thermal load.
In an E46 318i, combined consumption is ~8.0 L/100km (35 mpg UK). City driving may see 9–10 L/100km (31–28 mpg), while highway cruising can achieve ~6.5 L/100km (43 mpg). Real-world figures depend on driving style and vehicle condition.
Yes. The N42 series is an interference engine. If the timing chain fails or jumps, pistons can contact open valves, causing severe internal damage. Chain maintenance and tensioner inspection are critical, especially given the engine's high-RPM operation.
BMW specifies 10W-40 synthetic oil meeting BMW Longlife-98 spec. Change intervals should not exceed 15,000 km. Proper oil ensures adequate protection for camshafts, lifters, and the timing chain, especially under sustained high-RPM use.
Comprehensive technical documentation and regulatory references
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Regulation (EC) No 715/2007
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