3308708 - S01 ENGINE KNOCK

The engine makes a cyclical noise, the intensity of which varies with the load and is noticeable during brisk acceleration and when long ratios are used
Results of the tests
0PRELIMINARY CHECKSAll OKProblems metOperation
Disconnect the services belt and check whether the noise disappears.
Do not let the engine run for long with the belt disconnected
Press the clutch and check whether the noise disappears		 Continue to Step 1 The noise disappears when the services belt is disconnected See table   S10 
The noise only occurs with the clutch engaged See table   S20 
1CHECKING WITH DIAGNOSTIC EQUIPMENTAll OKProblems metOperation
Connect diagnostic equipment (Examiner or other instruments) to the diagnostic socket.

Verify:

  • that there are no faults in the engine management control unit
  • the plausibility of all the parameters
 Continue to Step 2 An error is detected in the control unitContinue following the instructions for the diagnostic equipment
Lack of dialogue with the control unit Restore the connection between the engine management control unit and the diagnostic connector ( See   E5050  DIESEL ENGINES ELECTRONIC MANAGEMENT ).
2CHECKING LOCATION OF KNOCKAll OKProblems metOperation
Carry out a test to locate the precise area from which the knocking is coming (if necessary, use suitable equipment)the knocking is not located: Continue to Step 3 The knocking is coming from the cylinder head Continue to Step 4
The knocking is coming from the cylinder block/crankcase Continue to Step 3
3KNOCKING CONDITION CHECKAll OKProblems metOperation
Carry out a test to identify the conditions in which the knocking from the cylinder block/crankcase occursThe knocking does not occur: Continue to Step 4 The knocking occurs with the engine cold and decreases during accelerationOverhaul the engine: in particular, check the condition of the pistons and replace them (see ENGINE OVERHAUL, Subassembly 1028)
The knocking occurs with the engine cold and increases during acceleration Overhaul the engine: in particular, check the condition of the main bearings and replace them: Op.   1024A10 
The knocking increases with the engine warmOverhaul the engine: check the condition of the gudgeon pins and replace them (see ENGINE OVERHAUL, Subassembly 1028)
The knocking disappears when the clutch is pressedOverhaul the engine: check the crankshaft end float (see ENGINE OVERHAUL, Subassembly 1004)
4CHECKING VALVE CLEARANCESAll OKProblems metOperation
Check that the valve tappet clearance is correct. Op.   1036H14  Continue to Step 5 Clearance not correct Restore the correct valve clearance. Op.   1036H18 
5CHECKING CYLINDER HEADAll OKProblems metOperation
Overhaul the cylinder head.

In particular, check:

  • that the cams are not worn
  • that the camshaft clearances are correct
  • the operation of the tappets
 Continue to Step 6 Cam worn or incorrect camshaft clearances Restore or replace the components involved Op.   1036B10 
6HECK ON CORRECT OPERATIONAll OKProblems metOperation
Check that the fault is no longer presentEnd of diagnosisFault persistsSearch for the fault starting from another symptom'