GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Timing Chain and Sprockets

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REMOVAL & INSTALLATION



2.3L and 2.4L Engines

See Figures 1 through 5


WARNING
The timing chain and sprockets on the 2.4L (VIN T) is not to be replaced with any other timing chain from any other model year than the one you are working on. In other words, if you have a 1996 model, ONLY a 1996 chain can be used. Failure to use the correct year chain will result in damage to the engine. The sprockets are different on the twin-cam engine and the shape of the links matches the sprockets for each year. It is recommended that this entire procedure be reviewed before attempting to service the timing chain.

The following tools will be required to perform this procedure:



Camshaft sprocket timing alignment pins-J 36008 or equivalent
 
Camshaft sprocket wrench-J 39579 or equivalent
 

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the front timing chain cover and crankshaft oil slinger (if equipped).
  4.  
  5. Rotate the crankshaft clockwise, as viewed from front of engine (normal rotation) until the camshaft sprocket's timing dowel pin holes align with the holes in the timing chain housing. The mark on the crankshaft sprocket should align with the mark on the cylinder block. The crankshaft sprocket keyway should point upwards and align with the centerline of the cylinder bores. This is the normal timed position.
  6.  



Click image to see an enlarged view

Fig. Fig. 1: View of the DOHC engine "timed position"-2.3L and 2.4L engines



Click image to see an enlarged view

Fig. Fig. 2: View of the SOHC engine "timed position"-2.3L engine

  1. Remove the timing chain guides. There are usually three.
  2.  
  3. Raise and safely support the front of the vehicle.
  4.  
  5. Make sure all of the slack is above the tensioner. Gently pry off timing chain tensioner spring retainer, then remove the spring.
  6.  

On the 2.3L engine two styles of tensioners are used. Early production engines will have a spring post and late production ones will not. Both styles are identical in operation and are interchangeable.

  1. Remove the timing chain tensioner shoe retainer.
  2.  
  3. Make sure all the slack in the timing chain is above the tensioner assembly; remove the chain tensioner shoe. The timing chain must be disengaged from the wear grooves in the tensioner shoe in order to remove the shoe. Slide a suitable small prybar under the timing chain while pulling shoe outward.
  4.  
  5. If difficulty is encountered while removing chain tensioner shoe, proceed as follows:
    1. Lower the vehicle.
    2.  
    3. Hold the intake camshaft sprocket with a camshaft sprocket wrench-J 39579 or equivalent holding tool and remove the sprocket bolt and washer.
    4.  
    5. Remove the washer from the bolt and re-thread the bolt back into the camshaft by hand. The bolt provides a surface to push against.
    6.  
    7. Remove intake camshaft sprocket using a 3-jaw puller in the 3 relief holes in the sprocket.
    8.  

  6.  

Do NOT try to pry the sprocket off the camshaft or damage to the sprocket or chain housing could occur.

  1. Unfasten the tensioner assembly attaching bolts, then remove the tensioner.
  2.  


CAUTION
The tensioner piston is spring loaded and could fly out causing personal injury. Use care when removing.

  1. Matchmark the timing chain outer surface for reassembly purposes.
  2.  
  3. If equipped, remove the chain housing to block stud, which is actually the timing chain tensioner shoe pivot.
  4.  
  5. Remove the timing chain.
  6.  
  7. Inspect the parts for wear, then replace if necessary. Some scoring of the timing chain shoe and guides is normal. Clean the old sealant off of the bolt with a wire brush. Clean the threaded hole in the camshaft with a round nylon bristle brush.
  8.  

To install:

WARNING
Failure to following installation procedures can result in severe engine damage.

  1. Install the intake camshaft sprocket onto the camshaft with the marked surface showing. Install the sprocket retaining bolt and washer. Use an adhesive compound 12345493 or equivalent on the bolt. Tighten the bolt to 52 ft. lbs. (70 Nm), while holding the sprocket with tool J-36013, J 39579 or equivalent, if removed.
  2.  
  3. Install tool J 36800 or equivalent, through hole(s) in the camshaft sprocket(s) into the holes in the timing chain housing. This positions the camshafts for correct timing.
  4.  



Click image to see an enlarged view

Fig. Fig. 3: Placing the camshaft sprockets onto the marked surface of the camshaft

  1. If the camshafts are out of position and must be rotated more than 1 /8 turn in order to install the alignment dowel pins:
    1. The crankshaft must be rotated 90° clockwise off of TDC in order to give the valves adequate clearance to open.
    2.  
    3. Once the camshafts are in position and the dowels installed, rotate the crankshaft COUNTERCLOCKWISE back to TDC.
    4.  

  2.  

Do NOT rotate the crankshaft clockwise to TDC, or valve and piston damage could occur.


WARNING
The side of the timing chain that was marked must be facing outward when installed.

  1. For DOHC engines only, install the timing chain over the exhaust camshaft sprocket, around the idler sprocket and around the crankshaft sprocket.
  2.  
  3. Remove the alignment dowel pin from the intake (DOHC only) camshaft. Using dowel pin remover tool J 39579 or equivalent, rotate the intake (DOHC only) camshaft sprocket counterclockwise enough to slide the timing chain over the intake (DOHC only) camshaft sprocket. Release the camshaft sprocket wrench. The length of chain between the two camshaft sprockets will tighten. If properly timed, the intake camshaft alignment dowel pin should slide in easily. If the dowel pin does not fully index, the camshafts are not timed correctly and the procedure must be repeated.
  4.  



Click image to see an enlarged view

Fig. Fig. 4: Place the timing chain over the exhaust camshaft and around the idler sprocket and around the crankshaft sprocketDOHC engines

  1. Leave the alignment dowel pins installed.
  2.  
  3. Raise and safely support the vehicle.
  4.  
  5. With slack removed from chain between intake camshaft sprocket (camshaft sprocket for SOHC engines) and crankshaft sprocket, the timing marks on the crankshaft and the cylinder block should be aligned. If marks are not aligned, move the chain one tooth forward or rearward, remove the slack and recheck the marks.
  6.  
  7. If equipped, tighten the chain housing to block stud. The stud is installed under the timing chain. Tighten to 19 ft. lbs. (26 Nm).
  8.  
  9. For vehicles through 1991, reload timing chain tensioner assembly to its "zero" position as follows:
    1. Assemble restraint cylinder, spring and nylon plug into plunger. Index slot in restraint cylinder with peg in plunger. While rotating the restraint cylinder clockwise, push the restraint cylinder into the plunger until it bottoms. Keep rotating the restraint cylinder clockwise but allow the spring to push it out of the plunger. The pin in the plunger will lock the restraint in the loaded position.
    2.  
    3. Install tool J-36589 or equivalent, onto plunger assembly.
    4.  
    5. Install plunger assembly into tensioner body with the long end toward the crankshaft when installed.
    6.  

  10.  
  11. For 1992-98 vehicles, reload timing chain tensioner assembly to its "zero" position as follows:
    1. Form a keeper from a piece of heavy gauge wire. See the accompanying figure.
    2.  
    3. Apply slight force on the tensioner blade to compress the plunger.
    4.  
    5. Insert a small prybar into the reset access hole, then pry the racket pawl away from the ratchet teeth while forcing the plunger completely in the hole.
    6.  
    7. Install the keeper between the access hole and the blade.
    8.  

  12.  



Click image to see an enlarged view

Fig. Fig. 5: View of reloading the timing chain tensioner assembly to its "zero" position-1992-98 vehicles

  1. Install the tensioner assembly to the chain housing. Recheck the plunger assembly installation. It is correctly installed when the long end is toward the crankshaft.
  2.  
  3. Install and tighten timing chain tensioner bolts. Tighten to 89 inch lbs. (10 Nm).
  4.  
  5. Install the tensioner shoe and tensioner shoe retainer. Remove the special tool J-36589, then squeeze the plunger assembly into the tensioner body to unload the plunger assembly.
  6.  
  7. Lower vehicle enough to reach and remove the alignment dowel pins.
  8.  
  9. Rotate crankshaft clockwise (normal rotation) two full rotations. Align the crankshaft keyway with the mark on the cylinder block, then reinstall the alignment dowel pins. The pins will slide in easily if the engine is timed correctly.
  10.  


WARNING
If the engine is not correctly timed, severe engine damage could occur.

  1. Install the timing chain guides and, if equipped, the crankshaft oil slinger.
  2.  
  3. Install the timing chain front cover. For details, please refer to the procedure located in this section.
  4.  
  5. Connect the negative battery cable, then start the engine and check for oil leaks.
  6.  

3.0L, 3.3L and 1990-91 2.5L Engines

See Figures 6 through 12

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the cooling system and the engine oil.
  4.  
  5. Remove the front timing cover. For details, please refer to the procedure located in this section.
  6.  



Click image to see an enlarged view

Fig. Fig. 6: View of the timing chain and sprockets, after the front cover has been removed-1986 3.0L engine shown

  1. With the engine at TDC, rotate the crankshaft to align the timing marks on the sprockets so that they are as close as possible.
  2.  
  3. Remove the timing chain damper assembly.
  4.  



Click image to see an enlarged view

Fig. Fig. 7: Remove the damper retainer, then ...



Click image to see an enlarged view

Fig. Fig. 8: ... remove the damper (damper) assembly

  1. Unfasten the camshaft sprocket-to-camshaft bolt(s), then remove the camshaft sprocket and chain and, if equipped, the thrust bearing.
  2.  



Click image to see an enlarged view

Fig. Fig. 9: Use the proper size socket to unfasten the camshaft sprocket bolts, then ...



Click image to see an enlarged view

Fig. Fig. 10: ... remove the camshaft sprocket and timing chain assembly

  1. Remove the crankshaft sprocket/gear by sliding it forward.
  2.  



Click image to see an enlarged view

Fig. Fig. 11: Extract the crankshaft sprocket from the crankshaft by sliding it forward

  1. Clean the gasket mounting surfaces. Inspect the timing chain and the sprockets for damage and/or wear, then replace any damaged parts.
  2.  

To install:
  1. Position the crankshaft so the No. 1 piston is at TDC of its compression stroke. On the 2.5L engine, install the thrust bearing.
  2.  
  3. Temporarily install the sprocket/gear on the camshaft, then position the camshaft so the timing mark on the gear is pointing straight down.
  4.  
  5. Assemble the timing chain to the gears so the timing marks are aligned, mark-to-mark.
  6.  



Click image to see an enlarged view

Fig. Fig. 12: Exploded view of the timing chain-3.0L engine

  1. Install the camshaft sprocket attaching bolt(s).
  2.  
  3. Install the camshaft thrust bearing, if not already done.
  4.  
  5. Install the timing chain damper.
  6.  
  7. Install the front cover and all related parts. For details, please refer to the procedure located in this section.
  8.  
  9. Connect the negative battery cable, then start the engine and check for leaks.
  10.  

3.1L Engine

See Figures 13, 14 and 15

  1. Disconnect the negative battery cable.
  2.  
  3. Drain the cooling system into a suitable container.
  4.  
  5. Remove the timing chain front cover. For details please refer to the procedure located in this section.
  6.  
  7. Rotate the crankshaft until the timing marks on the camshaft and crankshaft sprockets are in alignment at their closest approach.
  8.  



Click image to see an enlarged view

Fig. Fig. 13: Timing chain, sprockets and related components-1995 3.1L engine

  1. Unfasten the camshaft sprocket mounting bolt, then remove the camshaft sprocket and timing chain.
  2.  

If the sprocket does not come off easily, a light blow on the lower edge of the sprocket with a plastic mallet should dislodge it.

  1. Remove the crankshaft sprocket with gear puller J-5825-A, or equivalent.
  2.  



Click image to see an enlarged view

Fig. Fig. 14: Using a gear puller to remove the crankshaft sprocket

  1. Unfasten the two bolts and remove the timing chain damper.
  2.  

To install:
  1. Install the timing chain damper and tighten the mounting bolts to 15 ft. lbs. (21 Nm).
  2.  
  3. Position the crankshaft sprocket onto the crankshaft making sure the notch in the sprocket fits over the crankshaft key. Fully seat the sprocket on the crankshaft using J-38612, or an equivalent gear installer.
  4.  



Click image to see an enlarged view

Fig. Fig. 15: Use this type of installation tool to insert the crankshaft sprocket onto the crankshaft

  1. Apply prelube 1052367 or equivalent to the sprocket thrust surface.
  2.  
  3. Install the crankshaft timing chain damper to the cylinder block. Tighten the damper bolt to 15 ft. lbs. (21 Nm).
  4.  
  5. Align the timing mark on the crankshaft sprocket to the mark on the bottom of the timing chain damper.
  6.  
  7. Hold the camshaft sprocket with the timing chain hanging down.
  8.  
  9. Pick up the chain and sprocket and hold the sprocket in such a way that the timing mark is pointing down and the timing chain is hanging down off of the sprocket.
  10.  
  11. Loop the timing chain under the crankshaft sprocket and install the camshaft sprocket on the camshaft. The sprocket will only fit on the camshaft if the dowel on the camshaft lines up with the hole in the sprocket.
  12.  
  13. Verify the timing marks are aligned. If the marks are not in alignment proceed as follows:
    1. Remove the chain and sprocket.
    2.  
    3. Install the sprocket and mounting bolt loosely.
    4.  
    5. Rotate the crankshaft and camshaft until the marks are in alignment.
    6.  
    7. Remove the camshaft sprocket and mounting bolt.
    8.  

  14.  
  15. Repeat steps 13 and 14.
  16.  
  17. Tighten the camshaft sprocket mounting bolt to 74 ft. lbs. (100 Nm) on 1994-97 models and 103 ft. lbs. (140 Nm) on 1998 models.
  18.  
  19. Lubricate the timing chain components with engine oil.
  20.  
  21. Install the timing chain front cover.
  22.  
  23. Refill the cooling system.
  24.  
  25. Connect the negative battery cable, then start the engine and verify that there are no leaks.
  26.  

 
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