BMW Z3 1995-2002 2.5L Engine Specifications

The 2.5L engine (M52B25) in the 1995-2002 BMW Z3 features a straight-6 configuration, producing 170 horsepower at 5,500 RPM and 155 lb-ft of torque at 3,600 RPM. It has a displacement of 2,494 cc, with a bore of 84 mm and a stroke of 75 mm. The engine uses a DOHC valvetrain with 4 valves per cylinder, and it is paired with a 5-speed manual or 4-speed automatic transmission. It is compatible with premium unleaded gasoline and features a compression ratio of 10.5:1.

Regular maintenance for the 2.5L engine includes oil changes every 5,000-7,500 miles using synthetic oil (5W-30 or 5W-40). The timing belt should be replaced at 60,000 miles, and the water pump is typically replaced at the same time. Spark plugs should be replaced every 30,000 miles, and the coolant should be flushed and replaced every 50,000 miles. Brake fluid and transmission fluid should also be replaced at recommended intervals. Regular inspections of belts, hoses, and suspension components are advised.

Replacing parts on the 2.5L engine requires mechanical aptitude and specialized tools. For example, replacing the timing belt involves removing the lower cover, aligning the timing marks, and installing the new belt. Always refer to the service manual for specific instructions. Jack the car securely and ensure proper safety precautions are taken. For complex replacements like the engine or transmission, professional assistance is recommended. Always use genuine or OEM-equivalent parts to maintain performance and reliability.

Common issues with the 2.5L engine include oil leaks from the valve cover gasket, coolant leaks from the water pump, and VANOS system malfunctions. To diagnose, check for warning lights on the dashboard and review the fault codes using an OBD-II scanner. For oil leaks, inspect the valve cover and intake manifold gaskets. For coolant leaks, check the water pump and hoses. VANOS issues may require recalibration or replacement of the solenoid or seals. Always consult the service manual for detailed diagnostic procedures.

To optimize performance, consider upgrading the air intake system with a high-flow filter or cold air intake. Installing a performance exhaust system can improve power output and reduce backpressure. Tuning the engine with a reputable ECU tune can enhance horsepower and torque. Regular maintenance, such as spark plug replacements and fuel injector cleaning, also ensures optimal performance. For track use, lightweight components and suspension upgrades can improve handling and responsiveness.