Checking/diagnosis of crankcase ventilation system (with turbocharger) A20NFT/LHU
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Checking/diagnosis of crankcase ventilation system (with turbocharger) A20NFT/LHU
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Special tools
J 23951 Valve pressure gauge
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1.
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Check that the air cleaner is clean.
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2.
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Check that the oil filler cap is fitted in place.
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3.
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Check that the oil level indicator is fitted.
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4.
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Remove the oil level indicator. Fit a pressure gauge J 23951, or equivalent, in the oil level indicator tube.
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6.
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The vacuum at idling speed should provide a hydrostatic head of 3-4 1/2 inches height.
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7.
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If the vacuum is higher than this, check that the clean air hose from the camshaft cover to the air intake is not clogged or twisted, and check that the valve on the clean air hose is open when the vacuum from the engine is applied.
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8.
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The hose from the camshaft cover to the turbo is also used for the positive crankcase ventilation (PCV) and is used for PCV flow during normal operation and only PCV flow during turbocharging. If the hose is clogged the vacuum is increased. You can carry out the diagnosis by loosening the hose on the turbo side and starting the engine for a few seconds. It should create a large air leak and rough idle, which shows that there is an air flow. If the hose is clogged then the vacuum increases.
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9.
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If the vacuum level is normal, block or pinch the clean air hose. The clean air hose is the hose that runs between the camshaft cover and the air intake system. The vacuum should increase to about 5 inches in the pressure gauge. If you block the hose for too long the seals can be damaged.
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10.
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If the vacuum does not increase then the opening with a check valve in the centre of the intake manifold's side may be clogged.
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11.
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If the vacuum pressure or the pressure is zero, carry out a compression test.
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12.
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If the compression pressure is normal, check whether there is a clogged check valve outlet at the opening for the intake manifold.
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Problem
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Event
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External oil leakage
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Check to see if any of the following arises:
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Clogged induction system
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Clogged opening/check valve for positive crankcase ventilation (PCV) in the intake manifold
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Clogged or kinked PCV hoses
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Damaged or incorrectly fitted PCV hoses
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Crankcase pressure too high
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Clogged PCV hose from camshaft housing to turbo
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Rough idle
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Check to see if any of the following arises:
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Clogged or incorrectly fitted air intake system
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Clogged PCV opening/check valve in intake manifold
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Clogged or kinked PCV hoses
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Leaking or damaged PCV hoses
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Leaking PCV hose from camshaft housing to turbo
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Stalling or low idling speed
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Check to see if any of the following arises:
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Clogged induction system
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Clogged PCV opening in intake manifold
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Clogged or kinked PCV hoses
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Leaking or damaged PCV hoses
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Leaking PCV hose from camshaft housing to turbo
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High idling speed
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Check to see if any of the following arises:
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Air induction system correctly connected
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Leaking or damaged PCV hoses
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Sludge in the engine
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Check to see if any of the following arises:
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Clogged or incorrectly fitted air intake system
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Clogged PCV opening in intake manifold
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Clogged or kinked PCV hoses
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Clogged PCV hose from camshaft housing to turbo
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