22 · Diagnostics

Engine knock

Make: Fiat
Model: 500 Factory Service Manual
Year: 2007–2024
Section: Noise / vibrations › Engine knock

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Fault diagnosisEngine knock

ENGINE KNOCK

1.3 Multijet

The engine makes a cyclical noise - with the intensity varying according to the load - which is audible during brisk acceleration and when using long gear ratios.

1	CHECK USING DIAGNOSTIC EQUIPMENT	All OK	Problems encountered	Operation
		Test results
	Connect the Examiner diagnostic equipment to the diagnostic socket and check that there are no faults in the engine management control unit.	Move on to Step 2	Error detected in the engine management control unit.	Continue following the instructions on the diagnostic equipment
2	AUXILIARY UNITS CHECK	All OK	Problems encountered	Operation
	Disconnect the services belt and check whether the noise disappears Do not let the engine run for too long with the belt disconnected	Move on to Step 3	The noise disappears	Proceed as instructed in the See table S010 ENGINE WHILSTLING / SERVICES BELT NOISY
3	KNOCK LOCATION CHECK	All OK	Problems encountered	Operation
	Carry out a test to locate exactly the area where the knocking is coming from using special equipment.	Move on to Step 4	1. The knocking is coming from the cylinder head 2. The knocking is coming from the crankcase.	1. Move on to Step 5 2. Move on to Step 4
4	CRANKCASE KNOCK CHECK	All OK	Problems encountered	Operation
	Carry out a test to identify the circumstances in which the crankcase knock occurs.	Move on to Step 5	1. The knocking occurs with the engine cold and decreases when warm; when accelerating it is audible on overrun. 2. The knocking occurs with the engine cold and increases when the accelerator pedal is pressed to the floor and the gear ratio is long 3. The knocking is heard at all temperatures 4. The knocking is heard at all temperatures and decreases when the clutch pedal is pressed.	1. Overhaul the engine: in particular, check the condition of the pistons and, if necessary, replace them Op. 1028H20 PISTON WITH CONNECTING ROD - R.R 2. Overhaul the engine: in particular, check the condition of the main bearings and, if necessary, replace them Op. 1024A10 CRANKSHAFT - R.R WITH ENGINE REMOVED - CHECK AND, IF NECESSARY, REPLACE MAIN JOURNALS AND CRANKPINS 3. Overhaul the engine: in particular, check the condition of the connecting rod bearings and, if necessary, replace them Op. 1024A10 CRANKSHAFT - R.R WITH ENGINE REMOVED - CHECK AND, IF NECESSARY, REPLACE MAIN JOURNALS AND CRANKPINS 4. Overhaul the engine: in particular check for crankshaft judder.
5	TAPPET KNOCKING CHECK	All OK	Problems encountered	Operation
	If the vehicle is not often used, it is possible that an accentuated knocking of the tappets will be heard for a few minutes during start up, which will then gradually decrease.	Move on to Step 6	Tappet knocking persists.	Check operation of hydraulic tappets Op. 1036H57 HYDRAULIC TAPPETS (ALL) R.R and replace those that do not work.
6	CYLINDER HEAD CHECK	All OK	Problems encountered	Operation
	Overhaul the cylinder head and, in particular, check: no cam wear; cam axis clearance; valves and springs.	End of diagnosis	Cam wear or incorrect camshaft clearance	Repair or replace the components concerned.

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Parts & tools for this job For 2007 Fiat 500

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