BMW M52B25

The BMW M52B25 is a 2.5 liters (2,494 cc, 152.20 cu-in) straight-six, four-stroke cycle natural aspirated gasoline engine from BMW M52-family. The engine was manufactured on Munich Plant (Munich, Germany) from 1995 to 2000.

The M52B25 engine features a cast-aluminum alloy cylinder block with Nikasil coated cylinder liners. The aluminum cylinder head uses chain-driven double overhead camshafts (DOHC) and four valves per cylinder (24 valves in total). It is equipped with a Siemens MS 41.0, DME (Digital Motor Electronics) system, VANOS (Variable Valve Timing System from BMW) and a distributorless ignition system with individual ignition coils for each cylinder.

This engine has an 84.0 mm (3.31 in) cylinder bore and 75.0 mm (2.95 in) piston stroke. This engine has a compression ratio of 10.5:1 and a redline of 6,500 rpm. It produced 170 PS (125 kW; 168 HP) at 5,500 rpm of maximum horsepower and 245 N·m (25 kg·m, 180.6 ft·lb) at 3,950 rpm of peak torque.

The breakdown of the engine code is as follows:

• M52 – Engine Family
• B – Gasoline
• 25 – 2.5 Liter Displacement

General information

Cylinder block

The M52B25 cylinder block is cast aluminum alloy with Nikasil coated cylinder liners. Nikasil is a trademarked electrodeposited lipophilic nickel matrix silicon carbide coating for engine components. The cylinder bore is 84.0 mm (3.31 in) and the piston stroke is 75.0 mm (2.95 in). The cylinders are exposed on all sides to circulating coolant. The cast-iron counterweighted crankshaft rotates in replaceable split-shell main bearings. This engine used seven main bearings.

The forged steel connecting rods use replaceable split-shell bearings at the crankshaft end and solid bushings at the piston pin end. The pistons are of the three-ring type with two upper compression rings and a lower one-piece oil scraper ring. Full-floating piston pins are retained with circlips. The compression ratio rating is 10.5:1.

Cylinder head

The cylinder head is made of an aluminum alloy with good cooling efficiency. The M52B25 engine uses chain-driven double overhead camshafts and four valves per cylinder. Standart head height is 140.0 mm (5.5118 in). The cylinder head employs a crossflow design for greater power and efficiency. Intake air enters the combustion chamber from one side while exhaust gasses exit from the other. This engine is equipped with a single VANOS (Variable Camshaft Timing) system.

Intake valves are 33.0 mm (1.2992 in) in diameter and exhaust valves are 30.5 mm (1.2008 in). Valve clearance is set by self-adjusting (zero-lash) hydraulic lifters for reduced valve noise and the elimination of routine valve adjustment.

Head tightening procedure and torque specs:

• Step 1: 40.0 Nm; 4.1 kg·m; 29.5 ft·lb
• Step 2: Turn all bolts 90°
• Step 3: Turn all bolts another 90°

Maintenance data

Vehicle applications

Author: Sergei Wers
About: Co-founder and CEO of a multi-brand auto repair shop (engine repair, chassis repair, body repair and painting) for over 15 years. I have been developing internet sites with technical specifications for more than seven years.