Service Procedure

1. Using an Engine Ear J 39565 or an engine stethoscope listen to the area around the engine front cover and timing chain. It may be helpful to compare any noises with a vehicle that is known to have good or new timing chain and tensioner components. Timing chain noise is most often noted as a rattle or tick at idle speed that goes away at higher RPM. If the owner has a concern with engine noise and it does not appear to be related to the timing chain, review any service bulletins related to engine noise and Service Manual diagnostics related to engine noise conditions.

2. If timing chain noise is greater than normal, remove the engine front cover using procedures outlined in Section 6A2 or the Engine Section of the appropriate Service Manual.




3. Inspect the timing chain system for wear by measuring the distance between the hole in the tensioner bracket and the unworn surface of the tensioner shoe. (See Figure 1). If the distance between the hole and the tensioner shoe surface is more than 8 mm (0.314 in.), replacement of timing components is necessary.




4. Turn the crankshaft so that the timing marks on the crankshaft sprocket and the camshaft sprocket are aligned with the tabs on the timing chain tensioner bracket. (See Figure 2)

5. Remove the timing chain tensioner, timing chain, and both sprockets using the procedures outlined in Section 6A2 or the Engine Section of the appropriate Service Manual.




6. After removing the timing chain, tensioner, and sprockets, inspect the cup plug behind the timing chain for signs of oil flow (See Figure 3). The cup plug has an orifice approximately 1 mm (0.039 in.) in diameter. If the plug appears dry or the orifice appears to be blocked with debris, insent the puller end of slide hammer J 6471-02 or equivalent into the cup plug and remove it.

7. After cleaning any debris from behind the cup plug, install a new cup plug, GM P/N 14033197, into the oil passage.

Important:
The cup plug must be replaced with GM P/N 14033197. This plug has a specifically sized lubrication hole for the timing chain. If any other plug is used, there may be a reduction in engine oil pressure to the valvetrain or a lack of lubrication for the timing chain and tensioner components.

8. After the correct cup plug is installed in the oil passage, install a new timing chain, tensioner, and sprockets using procedures outlined in Section 6A2 or the Engine Section of the appropriate Service Manual.