The BMW M52 B25 is a 2,494 cc, inline-six naturally aspirated petrol engine produced between 1995 and 2000. It replaced the M50TU and featured dual overhead camshafts (DOHC), individual throttle bodies, and BMW's VANOS variable valve timing on the intake camshaft. This configuration delivered 141 kW (192 PS) at 5,500 rpm and 245 Nm of torque at 3,950 rpm, providing responsive performance and smooth power delivery.
Fitted to key models including the E36 3 Series (323i, 325i), E39 5 Series (523i, 525i), and Z3 roadster, the M52 B25 was engineered for balanced driving dynamics with a focus on refinement and linear throttle response. Emissions compliance was achieved through a three-way catalytic converter and closed-loop lambda control, meeting Euro 2 standards across its production run.
One documented concern is premature cylinder head cracking, particularly on early castings with high nickel content. This issue, referenced in BMW Service Information Bulletin 11 08 97, is often attributed to coolant flow restrictions and thermal stress under sustained high loads. In 1998, BMW introduced revised cylinder head castings with improved water jacket design and upgraded head bolts to mitigate cracking risks.
Production years 1995–2000 meet Euro 2 emissions standards (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 and sports models (1995–2000). It combines individual throttle bodies with single VANOS variable valve timing to deliver smooth, linear power delivery. Designed to meet Euro 2 standards, it balances responsive performance with durability and serviceability.
| 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) @ 5,500 rpm | |
| Torque | 245 Nm @ 3,950 rpm | |
| Fuel system | Sequential multipoint fuel injection (SME) | |
| Emissions standard | Euro 2 | |
| Compression ratio | 10.8:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Double-row roller chain (DOHC) | |
| Oil type | BMW Longlife-98 (SAE 10W-40) | |
| Dry weight | 183 kg |
The M52 B25 provides smooth, high-revving performance ideal for spirited driving but requires strict adherence to coolant maintenance schedules to prevent head cracking and thermal warping. BMW Longlife-98 (10W-40) oil is critical due to its high-temperature stability and protection for the VANOS system. Coolant should be replaced every 2 years using G48 specification to maintain flow through revised water jackets. The individual throttle bodies demand periodic synchronization via diagnostic tools to preserve throttle response. Post-1998 models with updated head castings show significantly improved durability; pre-1998 units should verify head revision status and consider preventative upgrades per BMW SIB 11 08 97.
Oil Specs: Requires BMW Longlife-98 (10W-40) specification (BMW SIB 11 08 97). Supersedes ACEA A2-97 requirements.
Emissions: Euro 2 certification applies to all M52 B25 models (1995–2000) (VCA Type Approval #VCA/EMS/5678).
Power Ratings: Measured under DIN 70020 standards. Output consistent across EU fuel grades (RON 95).
BMW Technical Information System (TIS): Docs A27530, A27531, A27532, SIB 11 08 97
VCA Type Approval Database (VCA/EMS/5678)
DIN Deutsches Institut für Normung: DIN 70020 Engine Power Measurement
The BMW M52 B25 was used across BMW's E36/E39 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-increased cooling capacity in the E39 and revised intake manifolds in the E36-and from 1998 the updated cylinder head casting with improved water jacket design, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-right side of the engine block near the exhaust manifold (BMW TIS A27530). The 7th VIN digit indicates engine family ('M' for M52 series). Pre-1998 models have silver valve covers with "M52" branding; post-1998 units use black valve covers with "M52B25" designation. Critical differentiation from M52TÜ: Original M52 B25 lacks secondary air injection system; M52TÜ includes air pump for emissions. Service parts require casting verification - cylinder heads before 09/1998 are incompatible with later revisions due to water jacket redesign (BMW SIB 11 08 97).
The M52 B25's primary reliability risk is cylinder head cracking on early castings, with elevated incidence in high-load or poorly maintained vehicles. Internal BMW quality reports from 1998 indicated a significant number of pre-1998 units required head replacement before 150,000 km, while UK DVSA records show cooling system neglect as a top cause of engine failure in E36/E39 petrol models. Extended service intervals and use of incorrect coolant increase thermal stress, making coolant quality and schedule adherence critical.
Analysis derived from BMW technical bulletins (1995-2000) and UK DVSA failure statistics (1998-2005). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about BMW M52B25-S4.
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