REMOVAL & INSTALLATION
Before attempting to remove the timing chain, read the entire procedure.
- Disconnect the negative battery cable.
- Remove the timing chain front cover, as outlined earlier in this section.
- Matchmark the timing chain and the sprockets outer surfaces for re-assembly. This is important to prevent noise and increased wear on the chain.
- Remove the timing chain guides.
- Make sure all of the slack in the timing chain is above the tensioner assembly, then remove the tensioner. The timing chain must be disengaged from any wear grooves in the tensioner shoe in order to remove the shoe. Slide a suitable prytool under the timing chain while pulling the shoe outward.
- Unfasten the tensioner assembly retaining bolts, then remove the tensioner.
If difficulty is encountered in removing the chain tensioner shoe, remove the intake camshaft sprocket, as follows;
- Hold the intake camshaft sprocket with a suitable tool and remove the sprocket bolt and washer.
- Remove the washer from the bolt and rethread the bolt back into the camshaft by hand. The bolt provides a surface to push against.
- Remove the camshaft sprocket using a three-jaw puller in the three relief holes in the sprocket.
- Rotate the crankshaft clockwise, as viewed from the front of engine/normal rotation, until the camshaft sprocket timing dowel pin holes line up with the holes in the timing chain housing. The crankshaft sprocket keyway should point upwards and line up with the centerline of the cylinder bores. This is the "timed" position.
- Mark the crankshaft sprocket and timing chain outer surface for reassembly, then remove the chain.
- Clean the old sealant off the bolt with a wire brush. Clean the threaded hole in the camshaft with a round nylon brush. Inspect the parts for wear and replace as necessary. Note that some scoring of the chain shoe and guides is normal.
- Position the camshaft sprockets onto the camshafts with the surface marked during removal showing.
- Install the camshaft sprocket retaining bolts and washers, tighten to 52 ft. lbs. (70 Nm) while holding each sprocket with a suitable tool. Use sealant on the camshaft sprocket bolts.
- Place camshaft aligning dowels or pins through the holes in the camshaft sprockets into the holes in the timing chain housing. This positions the cams for correct timing.
If the camshafts are out of position and must be rotated more than
turn in order to install the alignment dowel pins, proceed as follows:
- The crankshaft MUST be rotate 90° clockwise off of TDC in order to give the valves adequate clearance to open.
- Once the camshafts are in position and the dowels installed, rotate the crankshaft counterclockwise back to TDC.
- Place the timing chain over the exhaust camshaft sprockets, around the coolant pump sprocket and around the crankshaft sprocket.
- Remove the dowel from the intake camshaft. Rotate the sprocket counterclockwise enough to allow the timing chain to slide over the intake camshaft sprocket.
- Remove the slack from the chain between the intake camshaft sprocket and the crankshaft sprocket by lifting the chain as the tensioner would.
- With the slack removed from the chain between the intake camshaft sprocket and the crankshaft sprocket, the timing marks on the crankshaft and cylinder block should be aligned. If the marks are not aligned, move the chain one tooth forward or rearward, remove the slack and recheck the marks.
- Leave the alignment dowels in place.
Reload the timing chain tensioner assembly to its "zero" position as follows:
- With the tensioner plunger fully extended, turn the complete assembly upside down on a bench or other flat surface.
- Press firmly on the bottom of the tensioner housing.
- Compress the plunger until it is fully seated in the tensioner.
- Check the plunger length to make sure that it is sticking out of the cylinder the correct amount. Refer to accompanying photo.
- Loosely install the tensioner assembly to the timing chain housing. Finger tighten bolts.
- Install the timing chain tensioner shoe on the stud.
- Apply hand pressure to the timing chain tensioner shoe until the locking tab seats in the groove in the stud.
- Tighten the timing chain tensioner bolts to 89 inch lbs. (10 Nm). Do not overtighten.
Release the timing chain tensioner plunger.
- Using a small prytool or other suitable tool, press firmly against the face of the timing chain tensioner plunger.
- Depress the timing chain tensioner plunger until the plunger is bottomed out in the bore of the timing chain tensioner.
- Release the tensioner plunger. The plunger should press firmly against the back of the timing chain tensioner shoe.
- Remove the dowels from the camshaft sprockets.
- Rotate the crankshaft clockwise two full rotations. Align the crankshaft keyway with the mark on the cylinder block and reinstall the dowels. The dowels will slide in easily if the engine is timed correctly.
- Install the timing chain guides, then install the front (timing chain) cover.
- Connect the negative battery cable.
- Disconnect the negative battery cable.
- Drain the cooling system into a suitable container.
- Remove the timing chain front cover. For details, please refer to the procedure located in this section.
- Rotate the crankshaft until the timing marks on the camshaft and crankshaft sprockets are in alignment at their closest approach.
- Unfasten the camshaft sprocket mounting bolt, then remove the camshaft sprocket and timing chain together.
- Remove the crankshaft sprocket with gear puller.
- Unfasten the two bolts and remove the timing chain damper.
- Install the timing chain damper and tighten the mounting bolts to 15 ft. lbs. (21 Nm).
- 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 a gear installer.
- Apply prelube to the sprocket thrust surface.
- Install the crankshaft timing chain damper to the cylinder block. Tighten the damper bolt to 15 ft. lbs. (21 Nm).
- Align the timing mark on the crankshaft sprocket to the mark on the bottom of the timing chain damper. See the accompanying figure for timing mark reference.
- Hold the camshaft sprocket with the timing chain hanging down.
- 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.
- 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.
Verify the timing marks are aligned. See the accompanying figure for timing mark reference. If the marks are not in alignment proceed as follows:
- Remove the chain and sprocket.
- Install the sprocket and mounting bolt loosely.
- Rotate the crankshaft and camshaft until the marks are in alignment.
- Remove the camshaft sprocket and mounting bolt.
- Repeat steps 13 and 14.
- Tighten the camshaft sprocket mounting bolt to 103 ft. lbs. (140 Nm).
- Lubricate the timing chain components with engine oil.
- Install the timing chain front cover.
- Refill the cooling system.
- Connect the negative battery cable, then start the engine and verify that there are no leaks.