VQ25HR Engine Service and Repair Manual

VQ25HR Engine Service and Repair Manual provides comprehensive instructions for maintaining, diagnosing, and repairing the high-performance VQ25HR engine. It covers essential topics such as engine specifications, components breakdown, routine maintenance procedures, troubleshooting, and detailed repair guides. The manual is designed for both professional mechanics and car enthusiasts, featuring clear illustrations, step-by-step instructions, and technical data to ensure proper service and repair of the engine. Perfect for those working with the VQ25HR, it ensures reliability, performance, and longevity.

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• Engine type: V6, petrol, naturally aspirated
• Displacement: 2.5 liters (2495 cc)
• Power: ~225 hp (depending on model)
• Maximum torque: 243 Nm
• Configuration: DOHC (double overhead camshaft), V-angle 60°
• Cylinder diameter: 85.0 mm
• Piston stroke: 73.3 mm
• Compression ratio: 11.6:1
• Fuel system: Direct fuel injection system (DIS)
• Cooling: Liquid
• Cylinder block material: Aluminum alloy
• Gas distribution system: VVEL (Variable Valve Event and Lift) - valve timing and lift control system
• Ecological standard: Complies with Euro-4 standards

Cars that were equipped with the VQ25HR engine: Nissan Skyline М36, Fuga Н51, Infiniti G37 (V36)

This engine was installed mainly in premium Nissan models, providing a good combination of power, economy and reliability.

Timing chain wear:

Over time, the chain stretches, which can lead to poor engine performance and the appearance of extraneous noise.

Recommendation: Periodically check the condition of the chain and tensioners, especially at mileage over 150,000 km.

Oil leaks due to gaskets:

Valve cover gaskets can begin to leak over time, which will lead to oil leakage.

Recommendation: Watch for oil leaks, regularly check the oil level and replace the gaskets in a timely manner.

Problems with the VVEL (Variable Valve Event and Lift) system:

Sometimes there are malfunctions in the valve timing and lift system, which can cause uneven engine operation and loss of power.

Recommendation: Regularly service the VVEL system, monitor the serviceability of electric drives and valves.

Clogged Direct Injection System (DIS) injectors:

Poor quality fuel can cause injectors to become clogged, which will result in poor engine performance and increased fuel consumption.

Recommendation: Use high quality fuel and clean the injectors periodically.

Engine overheating:

Insufficient cooling can cause overheating, which can damage the cylinder head.

Recommendation: Check the coolant level regularly and monitor the condition of the radiator and thermostat.

Regular Oil and Filter Changes:

Use a quality engine oil that meets the manufacturer's specifications (usually 5W-30 or 5W-40). Change the oil every 7,500–10,000 km, along with changing the oil filter.

Cooling System Checks:

Periodically check the coolant level and condition. Change the coolant every 60,000–90,000 km or as recommended by the manufacturer.

Spark Plug Maintenance:

Replace spark plugs every 60,000–80,000 km. Use only the recommended spark plugs for this engine (iridium).

Intake System and Throttle Body Cleaning:

Periodically clean the throttle body and intake system to prevent carbon deposits from building up, which can reduce engine efficiency.

Checking and replacing belts and tensioners:

Regularly check the condition of the drive belts and their tension. If necessary, replace the tensioners and rollers to prevent belt failure.

Scheduled maintenance of the VVEL system:

Regularly check the operation of the variable valve timing and valve lift system. At the first sign of malfunction, contact the service.

Cleaning and diagnostics of injectors:

Clean the injectors every 30,000–40,000 km, especially if low-quality fuel is used.