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How to inspect, diagnose and replace a cylinder head.

Inspecting, diagnosing, and replacing a cylinder head on diesel engines like Cummins, Paccar, Detroit Diesel, Volvo, or Mack is a complex and involved process. It requires expertise, specialized tools, and knowledge of the specific engine model. Here is a general overview of the steps involved, but it is highly recommended to consult the engine manufacturer's service manual or a qualified technician for precise instructions:


  1. Visual Inspection: Start by visually inspecting the cylinder head for any visible signs of damage, cracks, warping, or leaks. Check for oil or coolant leaks, damaged gasket surfaces, or any other visible issues.

  2. Compression Testing: Perform a compression test on each cylinder to assess the cylinder head's sealing ability and overall engine health. Deviations in compression readings between cylinders may indicate a problem with the cylinder head or related components.

  3. Coolant Pressure Test: Perform a coolant pressure test to check for any leaks or external signs of coolant seepage from the cylinder head.


  1. Cylinder Leakage Test: Conduct a cylinder leakage test to identify any internal leaks within the combustion chamber. This test helps pinpoint potential issues such as damaged valves, valve seats, or head gasket failures.

  2. Combustion Gas Analysis: Analyze the combustion gas to detect any signs of coolant contamination, indicating a possible cylinder head or head gasket failure.


  1. Disconnection: Before replacing the cylinder head, disconnect the negative battery cable to prevent any electrical issues or accidental starting of the engine.

  2. Removal: Drain the coolant from the engine and remove any components obstructing access to the cylinder head, such as the intake and exhaust manifolds, fuel injectors, camshafts, and timing components. Carefully disconnect any wiring, sensors, hoses, and connections attached to the cylinder head. Loosen and remove the bolts securing the cylinder head to the engine block.

  3. Cleaning: Thoroughly clean the cylinder head mating surface and the engine block surface to ensure a proper seal when installing the new cylinder head. Remove any residue, old gasket material, or carbon deposits.

  4. Installation: Install the new cylinder head following the manufacturer's specifications and procedures. Use new gaskets, seals, and fasteners as recommended. Torque the head bolts to the specified values in the prescribed sequence.

  5. Reassembly: Reassemble the engine components, ensuring proper alignment and connection of all wiring, hoses, sensors, and components removed during the disassembly process.

  6. Fluid Refilling: Refill the engine with fresh coolant and engine oil, following the manufacturer's guidelines for the specific engine model.

  7. Testing and Verification: Start the engine and carefully monitor for any coolant or oil leaks, abnormal noises, or irregularities in engine performance. Perform additional checks such as compression tests and coolant pressure tests to verify the repair.

Please note that the exact steps and procedures can vary significantly depending on the specific engine model, manufacturer, and other factors. Always consult the appropriate service manual or seek assistance from qualified technicians for the specific engine and cylinder head you are working on.

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