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Home >> Kia >> 2004 >> Optima EX, 2.4 6 >> Repair and Diagnosis >> Engine Mechanical >> Timing Belt >> 2.4L 4-Cylinder Engine >> General >> Checking Compression Pressure

Checking Compression Pressure

  1. Before checking compression pressure, check the engine oil level. Make sure that the starter motor and battery are in normal operating condition.
  2. Start the engine and wait until engine coolant temperature reaches 80-95°C (176-205°F).
  3. Stop the engine and disconnect the spark plug cables.
  4. Remove the spark plugs.
  5. Crank the engine to remove any foreign material in the cylinders.
  6. Attach the compression gauge to the spark plug hole.
  7. Depress the accelerator pedal to fully open the throttle.
  8. Crank the engine and read the gauge.

    Limit :

    12.5 kg/ cm2 (1.23 MPa, 178 psi) [250-400 rpm]

    Fig 1: Checking Engine Compression
    G00326718Courtesy of KIA MOTORS AMERICA, INC.
  9. Repeat steps from 6 to 8 over all cylinders, making sure that the pressure differential for each of the cylinders is within the specified limit.

    Limit: Max :

    1.0 kg/cm2 (100 kpa, 14 psi) between cylinders

  10. If a cylinder's compression or pressure differential is below the specification, add a small amount of oil through the spark plug hole and repeat steps from 6 to 9.
    1. If the addition of oil brings the compression up, it is possible that there is wear between the piston ring and cylinder wall.
    2. If compression remains the same, valve seizure, poor valve seating or a compression leak from the cylinder head gasket are all possible causes.

      Tightening torque

      Spark plug : 20-30 Nm (200-300 kg.cm, 15-21 lb.ft)

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