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…
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 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.
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.
The most common questions about engine codes, what they mean, how to find them and how this database works
The M21 D24 (246TA) is fundamentally robust with strong mechanical integrity and proven longevity. Early models (1983–1984) had a known issue with timing belt tensioner wear, but the 1985 update (SIB 11 01 85) resolved this with a revised design. When maintained properly—using correct oil (SAE 10W-40) and adhering to 60,000 km timing belt intervals—these engines are highly durable and suitable for classic car ownership.
The most documented issues are timing belt failure (pre-1985), camshaft wear, cooling system leaks, and fuel injection problems. These are covered in BMW service documentation. While not all units fail, awareness and proactive maintenance—especially timing system care—can prevent major issues.
This 2.4L diesel engine was used in two generations: the E28 5 Series 524d (1983–1988) and the E30 3 Series 324d (1985–1988). It was BMW's first production diesel engine and was eventually superseded by the M51 engine family. It is part of BMW's legendary inline-six lineage.
Yes, the M21 D24 (246TA) can be tuned. Modifications like performance camshafts, high-flow exhaust, and upgraded intake manifolds can yield +15–25 kW. The stock internals are robust enough for mild upgrades. Classic builds often include turbocharger conversions or upgraded mechanical injection systems. However, ensure cooling and ignition systems are upgraded to handle increased output.
In real-world driving, expect 7.0–9.0 L/100km (40–31 mpg UK) in mixed conditions. Highway efficiency improves to ~6.5 L/100km (~43 mpg UK), while aggressive driving can exceed 10.0 L/100km (28 mpg UK). Fuel economy is consistent across E28 and E30 applications.
Yes, the M21 D24 (246TA) is an interference engine. If the timing belt fails or jumps, piston-to-valve contact is likely, resulting in severe internal damage. While the belt is designed for 60,000 km life, any signs of wear or age should prompt immediate replacement to prevent catastrophic failure.
BMW specifies SAE 10W-40 mineral oil for all M21 D24 (246TA) engines. This viscosity ensures proper lubrication of the camshaft and valvetrain under varied conditions. Change intervals are typically 6,000–10,000 km or annually. Using non-compliant oil can accelerate wear, especially in high-mileage engines.
Comprehensive technical documentation and regulatory references
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EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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