The BMW M40 B18 (184E1) is a 1,796 cc, inline-four naturally aspirated petrol engine produced from 1989 to 1994. Part of BMW's M40 engine family, it features a cast-iron block, aluminum head, and SOHC 8-valve configuration with belt-driven camshaft. Delivering 84 kW (115 PS) and 162 Nm of torque at 4,250 rpm, this engine was engineered for efficiency and reliability in compact executive sedans.
Installed in the E30 3 Series and early E36 3 Series models, the M40 B18 (184E1) served as a mainstream powerplant during a period of transition for BMW. It met emissions standards of the era (Euro 1 regulations) through Bosch Motronic 1.3 fuel injection, with catalytic converters fitted to all models for improved exhaust cleanliness. The engine is renowned for its mechanical simplicity and durability, forming a key part of BMW's entry-level petrol lineup.
In 1991, BMW issued Service Information Bulletin 11 02 91 addressing early reports of camshaft belt tensioner wear in high-mileage units. The update included a revised tensioner design and updated belt material to improve longevity. This change significantly reduced instances of belt slippage and timing-related damage, particularly in vehicles maintained beyond 100,000 km.
All production years 1989–1994 meet applicable Euro 1 emissions standards (VCA UK Type Approval #VCA/EMS/1840).
The BMW M40 B18 (184E1) is a 1,796 cc inline-four naturally aspirated petrol engine engineered for compact sedans (1989–1994). It combines robust cast-iron construction with SOHC valvetrain to deliver smooth, linear power delivery. Designed to meet Euro 1 emissions standards, it balances mechanical simplicity with driving refinement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,796 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 80.0 mm × 89.6 mm | |
| Power output | 84 kW (115 PS) @ 5,500 rpm | |
| Torque | 162 Nm @ 4,250 rpm | |
| Fuel system | Bosch Motronic 1.3 fuel injection | |
| Emissions standard | Euro 1 (catalyst-equipped) | |
| Compression ratio | 9.5:1 | |
| Cooling system | Water-cooled, belt-driven water pump | |
| Turbocharger | None | |
| Timing system | Single-row timing belt (replaced every 60,000 km) | |
| Oil type | SAE 10W-40 mineral oil | |
| Dry weight | 145 kg |
The M40 B18 (184E1)'s simplicity makes it highly durable when maintained properly. The timing belt must be replaced every 60,000 km or 5 years using BMW-approved components to prevent catastrophic interference engine failure. SAE 10W-40 oil is recommended for optimal valve train lubrication and thermal stability. The Bosch Motronic 1.3 system benefits from periodic sensor and injector cleaning. Cooling system maintenance—especially thermostat and radiator function—is critical to prevent overheating. Post-1991 models feature improved belt tensioner design; pre-1991 units should verify tensioner condition per BMW SIB 11 02 91.
Oil Specs: SAE 10W-40 mineral oil specified for all M40 B18 engines (BMW SIB 11 02 91). Synthetic oils not required due to low-stress design.
Emissions: Euro 1 certification applies to all models (1989–1994) (VCA Type Approval #VCA/EMS/1840). All units equipped with catalytic converters.
Power Ratings: Measured under DIN 70020 standards. Output consistent across Motronic 1.3 variants (BMW TIS Doc. A11013).
BMW Technical Information System (TIS): Docs A11013, SIB 11 02 91
VCA Type Approval Database (VCA/EMS/1840)
DIN 70020: German Standard for Engine Power Measurement
The BMW M40 B18 (184E1) was used across BMW's E30 and E36 platforms with longitudinal mounting. This engine received platform-specific adaptations-intake tuning in the E30 3 Series and emissions calibration in the E36 3 Series-and from 1991 received updated timing belt tensioner design to improve longevity, creating minor service part differences. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the right-side engine block near the transmission bellhousing (BMW TIS A11028). The 7th digit of the VIN indicates engine family ('M' for M-series). Pre-1991 models have a silver timing cover with standard tensioner; post-1991 units use a revised tensioner with improved spring design. Critical differentiation from M42: M40 B18 is an 8-valve SOHC engine, while M42 is a 16-valve DOHC performance unit. Service parts require production date verification—timing belts and tensioners for pre-1991 models are not identical to post-update units (BMW SIB 11 02 91).
The M40 B18 (184E1)'s primary reliability risk is timing belt failure due to neglected maintenance or use of non-OEM components. Internal BMW field reports from 1993 indicated a notable number of pre-1991 units suffering catastrophic engine damage before 120,000 km, while UK DVSA records show low rates of emissions-related failures due to effective catalyst management in later models. Extended high-RPM operation and inadequate cooling increase thermal stress, making timing and cooling system inspection critical.
Analysis derived from BMW technical bulletins (1989–1994) and UK DVSA failure statistics (1990–2000). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M40B18-184E1.
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Regulation (EC) No 715/2007
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