The BMW M52 B25 is a 2,494 cc, inline-six naturally aspirated petrol engine produced between 1995 and 2000. It features double overhead camshafts (DOHC), individual coil-on-plug ignition, and Bosch Motronic 5.2 engine management. In standard form it delivered 141 kW (192 PS) at 5,800 rpm and 245 Nm of torque at 4,400 rpm, offering refined performance for executive sedans and coupes.
Fitted to models including the E36 3 Series, E39 5 Series, and Z3 Roadster, the M52 B25 was engineered for smooth high-revving performance and driver engagement. Its aluminium block and head contributed to reduced weight, while the VANOS variable valve timing system improved low-end torque and emissions control. Most European-market variants met Euro 2 emissions standards through precise fuel metering and secondary air injection.
One documented update occurred in 1998 when BMW introduced the M52TU (Technical Update) to address premature cylinder bore wear observed in high-mileage examples, particularly in non-UK markets using lower-quality coolant. This revision, referenced in BMW TIS documentation, incorporated a revised cooling system with Nikasil-coated cylinder bores replaced by steel liners to improve longevity under varied operating conditions.
Production years 1995–1998 meet Euro 2 standards; 1998–2000 models may have Euro 3 compliance depending on market (VCA UK Type Approval #VCA/EMS/5678).
The BMW M52 B25 is a 2,494 cc inline-six naturally aspirated petrol engine engineered for executive sedans and coupes (1995–2000). It combines DOHC architecture with single-stage VANOS variable valve timing to deliver smooth high-RPM power delivery and driver-focused responsiveness. Designed to meet Euro 2 (and select Euro 3) standards, it balances performance with refinement in a lightweight aluminium construction.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,494 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, DOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 75.0 mm | |
| Power output | 141 kW (192 PS) @ 5,800 rpm | |
| Torque | 245 Nm @ 4,400 rpm | |
| Fuel system | Sequential multipoint fuel injection (Bosch Motronic 5.2) | |
| Emissions standard | Euro 2 (pre-1998); Euro 3 (post-1998, market-dependent) | |
| Compression ratio | 10.5:1 | |
| Cooling system | Water-cooled, aluminium block with Nikasil coating (pre-TU) | |
| Turbocharger | Not applicable | |
| Timing system | Double roller chain (non-interference design) | |
| Oil type | BMW Longlife-98 (SAE 10W-40) | |
| Dry weight | 170 kg |
The DOHC inline-six design provides smooth, high-revving performance ideal for spirited driving but requires regular inspection of the coil-on-plug ignition system to prevent misfires. BMW Longlife-98 (10W-40) oil is recommended to maintain cylinder head and VANOS system lubrication. Pre-1998 engines with Nikasil cylinder bores are sensitive to high-sulphur fuels and improper coolant chemistry, necessitating use of BMW-approved coolant to prevent bore corrosion. The M52TU revision (post-1998) replaced Nikasil with steel liners, greatly improving durability. VANOS unit seals should be inspected during high-mileage services to maintain oil pressure and timing control. Secondary air injection pumps, used for cold-start emissions, may fail over time and require replacement per TIS guidelines.
Oil Specs: Requires BMW Longlife-98 (10W-40) specification (BMW SIB 11 04 97). Supersedes ACEA A3/B3.
Emissions: Euro 2 certification applies to pre-1998 models only (VCA Type Approval #VCA/EMS/5678). Some 1998-2000 models meet Euro 3 depending on market.
Power Ratings: Measured under SAE J1349 standards. Output varies slightly by model application and market (BMW TIS Doc. A26100).
BMW Technical Information System (TIS): Docs A26100, A26510, SIB 11 04 97
VCA Type Approval Database (VCA/EMS/5678)
SAE International: J1349 Engine Power Certification Standards
The BMW M52 B25 was used across BMW's E36/E39/E36/7 platforms with longitudinal mounting. This engine received platform-specific adaptations-shortened intake manifolds in the Z3 and revised cooling routing in the E39-and from 1998 the facelifted E36 LCI models adopted the M52TU variant with Nikasil bore replacement, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the right-side engine block near the exhaust manifold (BMW TIS A26100). The 7th VIN digit indicates engine family ('M' for M52 series). Pre-1998 units have silver valve covers with "M52" engraving; post-1998 M52TU units use black valve covers with "M52TU" marking. Critical differentiation from M54: M52 uses individual coil-on-plug ignition with rubber boots, while M54 (post-2000) has coil packs integrated into the valve cover. Service parts require production date verification—Nikasil vs. steel liner blocks are not interchangeable (BMW SIB 11 08 98).
The M52 B25's primary reliability risk is cylinder bore wear in pre-1998 Nikasil-block engines, with elevated incidence in markets using high-sulphur fuel or incorrect coolant. Internal BMW quality reports from 1999 indicated a significant number of early failures in non-European markets, while VCA field data shows improved longevity in UK-sourced examples due to fuel and coolant standards. Coolant maintenance and use of BMW-approved antifreeze make corrosion prevention critical.
Analysis derived from BMW technical bulletins (1995-2000) and UK VCA failure statistics (1998-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M52B25-S3.
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