18 · Diagnostics

S12 Cyclic engine droning

Fault diagnosisS12 Cyclic engine droning

There is a constant, loud noise coming from the area of the engine, which is repeated at constant intervals

Step	Test procedure	Result	Action
1	CHECK AUXILIARY SHAFT BELT Check whether the whistling disappears when the belt is disconnected. NOTE: Do not let the engine run for long with the belt disconnected	OK	Move onto step 2
		The whistling disappears:	See table S10 ENGINE WHISTLING / UNIT BELT NOISE End of diagnosis
		The whistling remains constant	Move onto step 2
2	ALTERNATOR CHECK Check the alternator and, in particular condition of bearing that the pulley is correctly fixed	OK	Move onto step 3
		Alternator bearing damaged	Overhaul the alternator Op. 5530A18 End of diagnosis
		Pulley fixing not correct	Restore the correct pulley fastening Op. 5530A30 End of diagnosis
3	CHECK TIMING BELT TENSION Check the belt is not too taut	OK	Move onto step 4
3		Belt tension excessive	Restore correct tension End of diagnosis
4	CHECK TIMING BELT TENSIONER Check the belt tensioners and, in particular, the condition of the bearings	OK	Move onto step 5
		Fixed belt tensioner bearing damaged	Replace the fixed belt tensioner End of diagnosis
		Mobile belt tensioner bearing damaged	Change the mobile belt tensioner End of diagnosis
5	WATER PUMP CHECK Check the water pump and, in particular the condition of the bearing	OK	Move onto step 6
5		Water pump bearing damaged	Replace the water pump Op. 1088C10 End of diagnosis
6	CHECK ON CORRECT OPERATION Check that the fault is no longer present	OK	Incorrect selection of diagnostic procedure
6		Fault persists	Incorrect selection of diagnostic procedure

Parts & tools for this job For 2000 Alfa Romeo 147

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