Tools Required

Important: The timing chain housing to cylinder block and the camshaft housing gaskets can be replaced without removing the timing chain housing from the vehicle.

Removal of the timing chain housing is only required when additional service is being performed on the timing chain housing.
1. Disconnect the negative battery cable. Refer to

   Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

   in General Information.
2. Remove the engine front cover. Refer to Engine Front Cover Replacement .
3. Raise and support the vehicle. Refer to General Information.
4. Disconnect the heater hose from the thermostat housing in order to drain the cylinder block completely.

Important: The timing chain must be marked prior to removal. If the chain is installed with the wear pattern in the opposite direction, noise and increased wear may occur.

5. Remove the timing chain tensioner and timing chain. Refer to Camshaft Timing Chain, Sprocket, and Tensioner Replacement .
6. Remove the coolant pump assembly to the timing chain housing nuts. Refer to Coolant Pump Replacement in Engine Cooling.



7. Remove the timing chain housing to the block fasteners.
8. Remove the four oil pan to front cover bolts.
9. Remove the lowest front cover retaining stud from the timing chain housing.

This stud will catch on the body if it is not removed.

10. Lower the vehicle.



11. Remove the camshaft sprocket retaining bolts and the washers while holding the sprockets with the J 38122-A .
12. Remove the camshaft sprockets.

The camshaft sprockets are identical and interchangeable.




13. Remove the chain housing to the camshaft housing bolts.
14. Remove the timing chain housing and the gaskets.

It may be necessary to raise the engine slightly using the J 28467-360 .

15. Inspect the oil pan gasket silicone bead for the following conditions:

•	Cuts or nicks

•	Deformation

•	Separation from the aluminum carrier

16. If any of the conditions exist, replace the pan gasket.

Important: Use only enough sealant to restore the silicone bead to its original dimension. Excess application of sealant may cause part misalignment and oil leaks.

17. Inspect the silicone bead across the top of the aluminum carrier at the oil pan, in the cylinder block, and to the timing chain housing three way joint. Repair a damaged bead using the silicone rubber sealant GM P/N 12345739 or the equivalent.

1. Prior to installing the timing chain housing, ensure that the alignment dowel pins are in the cylinder block and the timing chain housing. The dowel pins ensure proper chain housing and the front cover location for correct front oil seal-to-crankshaft alignment.



2. Install the timing chain housing and the new gaskets. Gasket sealer is unnecessary.

Important: Hand tighten all chain housing bolts before tightening to specifications.




3. Install the chain housing to the camshaft housing bolts and hand tighten.
4. Raise and support the vehicle. Refer to General Information.
5. Install the timing chain housing block fasteners and hand tighten.
6. Install the oil pan to the timing chain housing bolts and hand tighten.



7. Tighten the timing chain housing block fasteners.

Tighten

•	(1) (M8 X 1.25 X 25) 26 N·m (19 lb ft).

•	(2) (M8 X 1.55 X 55) 50 N·m (37 lb ft).

•	(3) (M10 X 1.25 X 35) 29 N·m (21 lb ft).

Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.




8. Tighten the oil pan to the timing chain housing bolts.

Tighten

•	(1) (M8 X 1.25 X 80) 24 N·m (18 lb ft).

•	(2) (M8 X 1.24 X 22) 24 N·m (18 lb in).

•	(3) (M6 X 1.00 X 25) 12 N·m (106 lb ft).

•	(4) 26 N·m (19 lb ft).




9. Install the lowest front cover retaining stud into the timing chain housing.
10. Install the coolant pump to the timing chain housing and the timing chain housing nuts.

Tighten
Tighten the timing chain housing nuts to 26 N·m (19 lb ft).

11. Lower the vehicle.



12. Tighten the timing chain housing to the camshaft housing bolts.

Tighten

•	(1) (M8 X 1.25 X 25) 26 N·m (19 lb ft).

•	(2) (M10 X 1.55 X 55) 50 N·m (37 lb ft).

•	(3) (M8 X 1.25 X 35) 29 N·m (21 lb ft).




13. Install the camshaft sprockets.

The camshaft sprockets are identical and interchangeable.

14. Install the camshaft sprocket bolts and the washers.
15. Tighten the camshaft sprocket bolts and the washers while holding the sprocket with the J 38122-A .

Tighten
Tighten the camshaft sprocket bolts to 70 N·m (52 lb ft).

16. Use the Adhesive/Sealant Compound GM P/N 12345493 or the equivalent on the camshaft sprocket bolts.
17. Clean the old sealant off of the bolt with a wire brush.
18. Clean the threaded hole in the camshaft with a round nylon brush.
19. Clean the threaded hole in the camshaft with a round nylon brush.

Important: The side of the timing chain that was marked during the removal must be showing when the chain is installed.

20. Install the timing chain and the tensioner. Refer to Camshaft Timing Chain, Sprocket, and Tensioner Replacement .
21. Install the front cover and the gaskets. Refer to Engine Front Cover Replacement .
22. Connect the negative battery cable.