Subaru Engine FB25 2.5L Workshop Manual. EWD

This is a detailed guide to maintenance and repair of the Subaru FB25 2.5L engine. It contains:

✅ Specifications - design, parameters and main components of the engine.

✅ Fuel and injection system - device, diagnostics and maintenance.

✅ Timing and valve mechanism - timing chain, valve adjustment, valve timing.

✅ Cooling system - radiator, pump, thermostat, overheating problems.

✅ Lubrication system - oil pump, typical malfunctions, oil consumption.

✅ Diagnostics and error codes - decoding OBD-II codes, troubleshooting methods.

✅ Assembly and disassembly - step-by-step instructions with illustrations.

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The Subaru FB25 2.5L engine is a reliable, but not flawless unit. The main weak points and common malfunctions are listed below.

🔧 1. Increased oil consumption

Problem:

Over time, the engine begins to consume oil above the norm (1 liter per 1000 km or more).

The reason is the design features of the piston rings and cylinder wear.

Solution:

Use oil with a high alkaline number.

Replace the piston rings (sometimes it is necessary to reline the block).

🌡 2. Engine overheating

Problem:

Clogged radiator and insufficiently efficient cooling system.

Antifreeze leak through the cylinder head gasket (CHG).

Solution:

Regularly clean the radiator and replace the antifreeze every 60,000 km.

Check the condition of the CGB gaskets, replace if necessary.

🛠 3. Timing chain wear

Problem:

Timing chain stretching and tensioner wear by 150,000–200,000 km.

May cause incorrect valve timing.

Solution:

Check chain tension, replace if extraneous sounds appear.

⚠ 4. Carbon deposits on intake valves

Problem:

The lack of direct fuel injection leads to carbon deposits on the valves.

This reduces power and increases fuel consumption.

Solution:

Regular cleaning of valves (every 50,000–70,000 km).

Use of high-quality fuel and additives.

🔋 5. Ignition system malfunctions

Problem:

Ignition coils fail, engine misfires.

Solution:

Check the condition of the spark plugs every 30,000 – 50,000 km.

Replace the coils at the first signs of malfunction.