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Cylinder Leakage Test

If cylinder leakage equipment is available, a greater degree of diagnostic accuracy can be achieved. Pressure test each cylinder in turn and record % leakage. If leakage is exceptional from any one cylinder, try to determine the source of leakage, i.e. listen for air escaping into inlet manifold, exhaust manifold or crankcase. Leakage into exhaust manifold indicates exhaust valve poor sealing.

Preparation:

Follow test equipment manufacturers instructions.

Leakage results:

• less than 5% leakage indicates good valve / piston sealing.
• 5 to 10% leakage on all cylinders may indicate - general engine wear, multiple bent valves due to over-revving or previous timing belt problems.
• Over 10% leakage on single cylinder only, indicates poor sealing on this cylinder.

Compression Test

If cylinder leakage equipment is unavailable check each cylinder compression in turn with a compression tester.

Preparation:

• Ensure engine is hot.
• Crank engine for 6 seconds while testing each cylinder compression in turn.

Test results:

• If one cylinder pressure is lower than the others by more than 20 psi, this may indicate poor sealing on this cylinder.
• If all pressures are low, i.e. less than 150 psi, this may indicate general engine wear, multiple bent valves due to over-revving or previous timing belt problems.

If above tests confirm leakage problems, remove cylinder head and investigate further.

Cylinder Head Inspection

• Inspect cylinder bores for signs of scuffing or damage. If confirmed, renew piston and liner assemblies.
• Inspect cylinder head face around combustion chambers. If the cylinder head gasket fire rings have made a deep impression on head face, then this may indicate previous overheating. If repair history confirms this, cylinder head replacement should be considered.
• If no obvious cause of oil contamination is apparent from the areas described above, remove all valves (inlet and exhaust) from the affected combustion chamber and inspect valve heads closely for evidence of oil contamination and burning.

NOTE: Affected cylinder should have been determined following cylinder leakage / compression test.

• If when removed, a valve head shows no sign of burning, check that the valve stem is not bent. If it is, this will also result in poor valve sealing with similar symptoms.
• Look for likely causes of oil contamination, i.e. valve stem seals missing or damaged.

Cylinder Head Repair

• REPLACE ANY EXHAUST VALVES WHICH ARE BURNT ALONG WITH THE ADJOINING VALVE OF THE SAME COMBUSTION CHAMBER.
• GRIND IN NEW VALVES TO SEATS.
• RENEW ALL INLET AND EXHAUST VALVE STEM SEALS IN AFFECTED COMBUSTION CHAMBER.

Road test vehicle following repair to confirm engine running is acceptable.

Parts Information

LGH101190L - Exhaust valve (2 off required)

LUB100350L - Valve stem seal (4 off required)

Refer to parts fiche / electronic parts reader for appropriate gasket sets

Warranty