22 · Diagnostics

Engine knock

Make: Alfa Romeo
Model: 147 Factory Service Manual
Year: 2000–2004
Section: Noisy / vibrations › Engine knock

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Fault diagnosisEngine knock

ENGINE KNOCK

1.6 TS, 2.0 TS

The engine makes a cyclical noise, the intensity of which varies with the load and is noticeable during brisk acceleration and when long gear ratios are used

1	CHECKING WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
		Results of the tests
	Connect the diagnostic equipment to the diagnostic socket and check: that there are no faults in the engine management control unit	Continue to Step 2	An error is detected in the control unit	Continue following the instructions for the diagnostic equipment
2	CHECKING AUXILIARY COMPONENTS CHECK	All OK	Problems met	Operation
	Disconnect the service belt and check whether the noise disappears. Do not let the engine run for long with the belt disconnected	Continue to Step 3	The noise disappears	See table S10 ENGINE WHILSTLING / SERVICES BELT NOISY
3	CHECKING SITE OF KNOCKING	All OK	Problems met	Operation
	Carry out a test to locate the precise area from which the knocking is coming, using suitable equipment	Continue to Step 4	The knocking is coming from the cylinder head	Continue to Step 5
		Continue to Step 4	The knocking is coming from the cylinder block/crankcase	Continue to Step 4
4	CHECKING CRANKCASE KNOCK	All OK	Problems met	Operation
	Carry out a test to identify the conditions in which the knocking from the crankcase occurs.	Continue to Step 5	The knocking occurs with the engine cold, decreases with the engine hot and can be heard when releasing the accelerator.	Overhaul the engine, in particular check the condition of the pistons and replace them if necessary. Op. 1028H10
			The knocking occurs with the engine cold and increases during full acceleration with a long ratio.	Overhaul the engine: in particular, check the condition of the main bearings and replace them if necessary. Op. 1024A10
			The knocking is of a low intensity when cold but increases with the engine warm	Overhaul the engine: in particular, check the condition of the gudgeon pins and replace them. Op. 1028H60
			The knocking can be heard at all temperatures	Overhaul the engine: in particular, check the condition of the big end bearings and replace them if necessary Op. 1024A10
			The knocking can be heard at all temperatures and decreases when the clutch pedal is pushed.	Overhaul the engine and check the crankshaft end float.
5	CHECKING TAPPET KNOCK	All OK	Problems met	Operation
	If the car is not used frequently, an accentuated knocking sound may be heard from the tappets for a few minutes upon start up before gradually disappearing (see specific S.N.)	Continue to Step 6	Tappet knock persists	Continue to Step 6
6	CHECKING CYLINDER HEAD	All OK	Problems met	Operation
	Overhaul the cylinder head and, in particular, check the operation of the hydraulic tappets that the cams are not worn variable valve timing system camshaft clearane valves and springs	Continue to Step 7	Cam worn or incorrect camshaft clearances	Restore or replace the components involved
		Continue to Step 7	Tappets noisy	Check hydraulic tappet operation (as per standard procedure) and replace any that are not working
7	CHECKING CORRECT OPERATION	All OK	Problems met	Operation
	Check that the fault is no longer present		Fault persists	Search for the fault starting from another symptom'

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Parts & tools for this job For 2000 Alfa Romeo 147

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