MAN D26 Common Rail Engine - Repair and Maintenance Manual

The complete repair manual for the MAN D26 Common Rail engine is intended for mechanics, truck owners and service centers. Here you will find:

• Detailed information on disassembling and assembling the MAN D2676 engine
• Technical specifications, torque, valve clearances
• Diagrams of the Common Rail system, fuel and oil circuit
• Installation procedure for injectors, injection pump, turbocharger, EGR
• Frequent faults and diagnostic methods
• Compliance with environmental standards Euro 4/5/6

The manual covers all key components: cylinder block, cylinder head, crankshaft, attachments, electrical equipment, cooling and lubrication.

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Where the MAN D26 engine is used:

• MAN TGX, TGS trucks
• MAN Lion's Coach / Lion's Intercity buses
• Special equipment: agricultural machinery, quarry dump trucks, etc.

🔧 1. Common Rail fuel system problems

Symptoms: difficult starting, loss of power, uneven operation, injector errors.

Causes:

Injector wear (misfires)

Air leak in the return line

System contamination (water, dirt)

Injection pump wear (high pressure pump)

✅ Prevention:

• Regularly change fuel filters (every 60–80 thousand km)
• Use high-quality fuel
• Check pipeline tightness
• Diagnose rail pressure

🔧 2. EGR valve and intake manifold coking

Symptoms: black smoke, loss of power, overheating, air errors.

Causes:

Soot deposits during frequent short trips

Poor fuel and oil quality

✅ Prevention:

• Regular cleaning of EGR and intake manifold
• Use of oil with MAN M3277/M3677 approval
• Maintaining correct operation of the turbocharging system

🔧 3. Turbine problems

Symptoms: whistling, loss of power, increased oil consumption

Causes:

Overheating and oil starvation

Dirt in oil lines

Problems in the crankcase ventilation system

✅ Prevention:

• Oil change every 40–50 thousand km
• Do not turn off the engine immediately after loading (let the turbine cool down)
• Checking the crankcase ventilation

🔧 4. Wear or destruction of camshafts and rockers

Symptoms: noise in the cylinder head, unstable engine operation, vibration

Causes:

Lack of lubrication

Violation of oil change interval

Overload

✅ Prevention:

• Checking oil level
• Using oil with MAN approvals
• Checking valve clearances (adjustment every 150–200 thousand km)

🔧 5. Problems with the crankcase ventilation system (CVCS)

Symptoms: oil squeezing out, leaking from seals, increased oil consumption

Causes:

Clogging of the oil separator

Freezing of ventilation tubes in winter

✅ Prevention:

• Cleaning or replacing the CVCS every 150–200 thousand km
• Using winter oil in the cold season

🔧 6. Increased oil consumption

Symptoms: frequent oil topping up, blue smoke

Causes:

Worn piston rings

Problems with the turbine

Leaks along the gaskets

✅ Prevention:

• Compression control
• Tightness check
• Monitoring via diagnostic software