Tools Required

Important: You can replace the timing chain housing-to-cylinder block gasket and the camshaft housing gasket 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 Cautions and Notices.
2. Drain the cooling system. Refer to Cooling System Draining and Filling in Engine Cooling.
3. Remove the engine front cover. Refer to Engine Front Cover Replacement .
4. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle General Information.
5. 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.

6. Remove the timing chain tensioner and timing chain. Refer to Camshaft Timing Chain, Sprocket, and Tensioner Installation .
7. Remove the nuts which secure the coolant pump assembly to the timing chain housing. Refer to Water Pump Replacement in Engine Cooling.



8. Remove the fasteners which secure the timing chain housing to the block.
9. Remove the 4 bolts which secure the oil pan to the front cover.
10. Remove the lowest front cover retaining stud from the timing chain housing, in order to prevent catching on the body.
11. Lower the vehicle.



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

The camshaft sprockets are identical and interchangeable.




14. Remove the bolts which secure the chain housing to the camshaft housing.
15. Remove the timing chain housing and the gaskets.

You may need to raise the engine slightly using the J 28467-360 . Refer to Engine Support Fixture .

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

•	Cuts or nicks

•	Deformation

•	Separation from the aluminum carrier

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

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

18. 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 3-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 bolts which secure the chain housing to the camshaft housing. Hand tighten the bolts.
4. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
5. Install the timing chain housing block fasteners and hand tighten.
6. Install the bolts which secure the oil pan to the timing chain housing. Hand tighten the bolts.




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.

7. Tighten the timing chain housing block fasteners as shown in the illustration.

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).




8. Tighten the bolts which secure the oil pan to the timing chain housing, as shown in the illustration.

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. Install 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 bolts which secure the timing chain housing to the camshaft housing, as shown in the illustration.

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. Use the Adhesive/Sealant Compound GM P/N 12345493 or the equivalent on the camshaft sprocket bolts.
15. Install the camshaft sprocket bolts and the washers.
16. 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).

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.