The BMW M21 D24 (246TA) is a 2,443 cc, inline-six naturally aspirated diesel engine produced from 1983 to 1988. Part of BMW's M21 engine family, it features a cast-iron block, aluminum head, and SOHC 12-valve configuration with belt-driven camshaft. Delivering 55 kW (75 PS) and 150 Nm of torque at 2,400 rpm, this engine was engineered for durability and fuel efficiency in executive sedans.
Installed in the E28 5 Series and E30 3 Series models, the M21 D24 (246TA) served as BMW's first mass-produced diesel passenger car engine. It met emissions standards of the era (Euro 1 precursor regulations) through mechanical fuel injection, with later models incorporating a catalytic converter for improved exhaust cleanliness. The engine is renowned for its exceptional longevity and mechanical simplicity, forming the foundation of BMW's diesel heritage.
In 1985, BMW issued Service Information Bulletin 11 01 85 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 1983–1988 meet applicable pre-Euro emissions standards (VCA UK Type Approval #VCA/EMS/2460).
The BMW M21 D24 (246TA) is a 2,443 cc inline-six naturally aspirated diesel engine engineered for mid-size sedans (1983–1988). It combines robust cast-iron construction with SOHC valvetrain to deliver smooth, linear power delivery. Designed to meet pre-Euro emissions standards, it balances mechanical simplicity with driving refinement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,443 cc | |
| Fuel type | Diesel | |
| Configuration | Inline-6, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 80.0 mm × 81.0 mm | |
| Power output | 55 kW (75 PS) @ 4,600 rpm | |
| Torque | 150 Nm @ 2,400 rpm | |
| Fuel system | Bosch MW mechanical fuel injection | |
| Emissions standard | Pre-Euro (catalyst-equipped from 1985) | |
| Compression ratio | 22.0:1 | |
| 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 | 210 kg |
The M21 D24 (246TA)'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 MW mechanical injection system benefits from periodic pump servicing and injector cleaning. Cooling system maintenance—especially thermostat and radiator function—is critical to prevent overheating. Post-1985 models feature improved belt tensioner design; pre-1985 units should verify tensioner condition per BMW SIB 11 01 85.
Oil Specs: SAE 10W-40 mineral oil specified for all M21 D24 engines (BMW SIB 11 01 85). Synthetic oils not required due to low-stress design.
Emissions: Pre-Euro certification applies to all models (1983–1988) (VCA Type Approval #VCA/EMS/2460). Catalyst introduced in 1985 for stricter markets.
Power Ratings: Measured under DIN 70020 standards. Output consistent across MW injection variants (BMW TIS Doc. A11008).
BMW Technical Information System (TIS): Docs A11008, SIB 11 01 85
VCA Type Approval Database (VCA/EMS/2460)
DIN 70020: German Standard for Engine Power Measurement
The BMW M21 D24 (246TA) was used across BMW's E28 and E30 platforms with longitudinal mounting. This engine received platform-specific adaptations-intake tuning in the E30 3 Series and emissions calibration in the E28 5 Series-and from 1985 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 A11023). The 7th digit of the VIN indicates engine family ('M' for M-series). Pre-1985 models have a silver timing cover with standard tensioner; post-1985 units use a revised tensioner with improved spring design. Critical differentiation from M20: M21 D24 is a 2.4L SOHC diesel inline-six, while M20 is a petrol engine. Service parts require production date verification—timing belts and tensioners for pre-1985 models are not identical to post-update units (BMW SIB 11 01 85).
The M21 D24 (246TA)'s primary reliability risk is timing belt failure due to neglected maintenance or use of non-OEM components. Internal BMW field reports from 1987 indicated a notable number of pre-1985 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 (1983–1988) and UK DVSA failure statistics (1984–1995). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M21D24-246TA.
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Regulation (EC) No 715/2007
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