Timing Chain: Service and Repair
Camshaft Timing Chain, Sprockets, and Tensioner Replacement
1. Disconnect the negative battery cable.
2. Remove the No. 1 cylinder spark plug. Refer to Spark Plug Replacement Service and Repair.
3. Rotate the crankshaft in the engine rotational direction clockwise, until the No. 1 piston is at top dead center (TDC) on the compression stroke.
4. Raise and support the vehicle.
5. Remove the engine front cover. Refer to Engine Front Cover Replacement Service and Repair.
6. Lower the vehicle.
7. Remove the camshaft cover. Refer to Camshaft Cover Replacement Service and Repair.
Important: The timing chain tensioner must be removed to unload chain tension before the timing chain is removed. If not removed, the timing chain will become cocked and it will be difficult to remove.
8. Remove the timing chain tensioner.
9. Remove the upper timing chain guide.
10. Use a 24 mm wrench to hold the camshafts from turning.
11. Remove the exhaust camshaft sprocket bolt and discard.
12. Remove the exhaust camshaft sprocket.
13. Remove the timing chain tensioner guide.
14. Remove the engine mount. Refer to Engine Mount Bracket Replacement. Engine Mount Strut Bracket Replacement
15. Remove the fixed timing chain guide access plug.
16. Remove the fixed timing chain guide.
17. Remove the intake camshaft sprocket bolt and discard.
18. Remove the intake camshaft sprocket.
19. Remove the timing chain through the top of the cylinder head.
20. Remove the crankshaft sprocket.
21. Remove the oil nozzle and bolt.
22. Remove the balance shaft drive chain tensioner.
23. Remove the adjustable balance shaft chain guide.
24. Remove the small balance shaft drive chain guide.
25. Remove the upper balance shaft drive chain guide.
Important: It may ease removal of the balance shaft drive chain to get all of the slack in the chain between the crankshaft and water pump sprockets.
26. Remove the balance shaft drive chain.
Timing Balance Shafts to Engine
1. Install the balance shaft drive sprocket.
Important: If the balance shafts are not properly timed to the engine, the engine may vibrate or make noise.
2. Install the balance shaft drive chain with the colored links lined up on with the marks on the balance shaft drive sprockets and the crankshaft sprocket. There are three colored links on the chain. Two links are of matching colors, and one link is of a unique color. Use the following procedure to line up the links with the sprockets.
Orient the chain so that the colored links are visable.
3. Place the uniquely colored link (1) so that it lines up with the timing mark on the intake side balance shaft sprocket.
4. Working clockwise around the chain, place the first matching colored link (2) in line with the timing mark on the crankshaft drive sprocket. (approximately 6 o'clock position on the crank sprocket)
5. Place the chain (3) on the water pump drive sprocket. The alignment is not critical.
6. Align the last matching colored link (4) with the timing mark on the exhaust side balance shaft drive sprocket.
Installation Procedure
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.
Important: If the balance shafts are not properly timed to the engine, the engine may vibrate and make noise.
1. Install the upper balance shaft chain guide.
Tighten
Tighten the upper balance shaft chain guide bolts to 15 Nm (133 lb in).
2. Install the small balance shaft chain guide.
3. Tighten the balance shaft chain guide bolts.
Tighten
Tighten the chain guide bolts to 10 Nm (89 lb in).
4. Install the adjustable balance shaft drive chain guide.
Tighten
Tighten the chain guide bolts to 10 Nm (89 lb in).
5. Turn the tensioner plunger 90 degrees in its bore and compress the plunger until a paper clip can be inserted through the hole in the plunger body and into hole in the tensioner plunger.
6. Install the timing chain tensioner.
7. Tighten the chain tensioner bolts.
Tighten
Tighten the chain tensioner bolts to 10 Nm (89 lb in).
8. Remove the paper clip from the balance shaft drive chain tensioner.
9. Install the oil nozzle and bolt.
Tighten
Tighten the oil nozzle bolt to 10 Nm (89 lb in).
10. Install the crankshaft sprocket with timing mark at the 5 o'clock position.
11. Lower the timing chain through the opening in the top of the cylinder head. Carefully ensure that the chain goes around both sides of the cylinder block bosses (1, 2).
12. Install the intake camshaft sprocket with the INT diamond at the 2 o'clock position.
13. Hand tighten a NEW intake camshaft sprocket bolt.
14. Route the timing chain around the crankshaft sprocket with the matching colored link aligning with the timing mark.
15. Route the timing chain around the intake camshaft sprocket with the uniquely colored link (1) aligning with the INT diamond.
16. Install the timing chain tensioner guide through the opening in the top of the cylinder head.
Tighten
Tighten the timing chain tensioner guide bolt to 10 Nm (89 lb in).
17. Install the exhaust camshaft sprocket with the timing chain matching colored link (3) at EXH triangle aligned at the 10 o'clock position.
18. Use a 24 mm wrench to rotate the camshaft slightly, until exhaust sprocket aligns with the camshaft.
19. Hand tighten the NEW exhaust camshaft sprocket bolt.
20. Install the fixed timing chain guide.
Tighten
Tighten the fixed timing chain bolts to 15 Nm (133 lb in).
21. Verify that all the colored links are aligned with the appropriate exhaust (1), intake (2), and crankshaft marks (3).
22. Apply sealant, GM P/N 12345382 (Canadian P/N 10953489) to thread and install the timing chain guide bolt access hole plug.
Tighten
Tighten the access hole plug to 90 Nm (66 lb ft).
23. Install the engine mount. Refer to Engine Mount Bracket Replacement. Engine Mount Bracket Replacement
24. Inspect the timing chain tensioner. If the timing chain tensioner, O-ring seal, or washer is damaged, replace the timing chain tensioner.
25. Measure the timing chain tensioner assembly from end to end.
A new tensioner should be supplied in the fully compressed non-active state. A tensioner in the compressed state will measure 72 mm (2.83 in) (a) from end to end. A tensioner in the active state will measure 85 mm (3.35 in) (a) from end to end.
26. If the timing chain tensioner is not in the compressed state, perform the following steps:
26.1 Remove the piston assembly from the body of the timing chain tensioner by pulling it out.
26.2 Install the J 45027-2 (2) into a vise.
26.3 Install the notch end of the piston assembly into the J 45027-2 (2).
26.4 Using the J 45027-1 (1), turn the ratchet cylinder into the piston.
27. Inspect the bore of the tensioner body for dirt, debris, and damage. If any damage appears, replace the tensioner. Clean dirt or debris out with a lint free cloth.
28. Install the compressed piston assembly back into the timing chain tensioner body until it stops at the bottom of the bore. Do not compress the piston assembly against the bottom of the bore. If the piston assembly is compressed against the bottom of the bore, it will activate the tensioner, which will then need to be reset again.
29. At this point the tensioner should measure approximately 72 mm (2.83 in) (a) from end to end. If the tensioner does not read 72 mm (2.83 in) (a) from end to end repeat steps 25.1 and 25.4.
30. Inspect to ensure all dirt and debris is removed from the timing chain tensioner threaded hole in the cylinder head.
31. Install the new timing chain tensioner assembly.
Tighten
Tighten the timing chain tensioner to 75 Nm (55 lb ft).
32. The timing chain tensioner is released by compressing it 2 mm (0.079 in) which will release the locking mechanism in the ratchet. To release the timing chain tensioner, use a suitable tool with a rubber tip on the end. Feed the tool down through the cam drive chest to rest on the cam chain. Then give a sharp jolt diagonally downwards to release the tensioner.
33. Use a 24 mm wrench to hold the camshaft.
Tighten
Tighten the NEW camshaft bolts to 85 Nm (63 lb ft) plus 30 degrees.
34. Install the upper timing chain guide.
Tighten
Tighten the upper chain guide bolts to 10 Nm (89 lb in).
35. Install the camshaft cover. Refer to Camshaft Cover Replacement Service and Repair.
36. Raise the vehicle.
37. Install the engine front cover. Refer to Engine Front Cover Replacement Service and Repair.
38. Lower the vehicle.
39. Connect negative battery cable.