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The valve train includes roller tappet assemblies, aligning yokes and yoke retainer.
Roller tappet alignment is maintained by machined flats on tappet body being fitted in pairs into six aligning yokes. The yokes are secured by an alignment yoke retainer (Fig. 26).
Fig. 26 Roller Tappets Aligning Yoke and Retainer
Before disassembling any part of the engine to correct tappet noise, read the oil pressure at the gauge. Install a reliable gauge at pressure sending unit if vehicle has no oil pressure gauge and check the oil level in the oil pan. The pressure should be between 30 and 80 psi (206.8 to 551.6 kPa) at 2000 rpm.
The oil level in the pan should never be above the MAX mark on dipstick, or below the MIN mark. Either of these two conditions could be responsible for noisy tappets. Oil Level Check: stop engine after reaching normal operating temperature. Allow 5 minutes to stabilize oil level, check dipstick.
If oil level is above the MAX mark on dip stick, it is possible for the connecting rods to dip into the oil while engine is running and create foam. Foam in oil pan would be fed to the hydraulic tappets by the oil pump causing them to become soft and allow valves to seat noisily.
Low oil level may allow pump to take in air which when fed to the tappets, causes them to become soft and allows valves to seat noisily. Any leaks on intake side of pump through which air can be drawn will create the same tappet action. Check the lubrication system from the intake strainer to the pump cover, including the relief valve retainer cap. When tappet noise is due to aeration, it may be intermittent or constant, and usually more than one tappet will be
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noisy. When oil level and leaks have been corrected, engine should be operated at fast idle to allow all of the air inside of the tappets to be bled out.
To determine source of valve train noise, operate engine at idle with cylinder head covers removed and listen for source of the noise.
Worn valve guides or cocked springs are sometimes mistaken for noisy tappets. If such is the case, noise may be dampened by applying side thrust on the valve spring. If noise is not appreciably reduced, it can be assumed the noise is in the tappet. Inspect the rocker arm push rod sockets and push rod ends for wear.
Valve tappet noise ranges from light noise to a heavy click. A light noise is usually caused by excessive leakdown around the unit plunger which will necessitate replacing the tappet, or by the plunger partially sticking in the tappet body cylinder. A heavy click is caused either by a tappet check valve not seating, or by foreign particles becoming wedged between the plunger and the tappet body causing the plunger to stick in the down position. This heavy click will be accompanied by excessive clearance between the valve stem and rocker arm as valve closes. In either case, tappet assembly should be removed for inspection and cleaning.
(1)Refer to Cylinder Head Removal of this section to remove intake manifold and cylinder heads for access to tappets for service.
(2)Remove yoke retainer and aligning yokes.
(3)Use Tool C-4129 to remove tappets from their bores. If all tappets are to be removed, identify tappets to insure installation in original location.
If the tappet or bore in cylinder block is scored, scuffed, or shows signs of sticking, ream the bore to next oversize and replace with oversize tappet.
CAUTION: The plunger and tappet bodies are not interchangeable. The plunger and valve must always be fitted to the original body. It is advisable to work on one tappet at a time to avoid mixing of parts. Mixed parts are not compatible. Do not disassemble a tappet on a dirty work bench.
(1)Pry out plunger retainer spring clip.
(2)Clean varnish deposits from inside of tappet body above plunger cap.
(3)Invert tappet body and remove plunger cap, plunger, flat or ball check valve, check valve spring, check valve retainer and plunger spring. Check valve could be flat or ball.
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Fig. 27 Hydraulic Roller Tappet Assembly
(1)Clean all tappet parts in a solvent that will remove all varnish and carbon.
(2)Replace tappets that are unfit for further service with new assemblies.
(3)If plunger shows signs of scoring or wear, valve is pitted, or valve seat on end of plunger indicates any condition that would prevent valve from seating, install a new tappet assembly.
(4)Assemble tappets (Fig. 27).
(1)Lubricate tappets.
(2)Install tappets in their original positions.
(3)With roller tappets, install aligning yokes with (Fig. 26).
(4)Install yoke retainer and torque screws to 12 Nzm (105 in. lbs.) (Fig. 26).
(5)Install cylinder heads. Refer to cylinder head installation of this section for procedure.
(6)Start and operate engine. Warm up to normal operating temperature.
CAUTION: To prevent damage to valve mechanism, engine must not be run above fast idle until all hydraulic tappets have filled with oil and have become quiet.
(1)Remove front valve cover and all 6 spark plugs.
(2)Rotate engine until the #2 piston is at TDC of the compression stroke.
(3)Install a degree wheel on the crankshaft pulley.
(4)With proper adaptor, install a dial into #2 spark plug hole. Using the indicator find TDC on the compression stroke.
(5)Position the degree wheel to zero.
(6)Remove dial indicator from spark plug hole.
(7)Place a 5.08mm (.200 inch) spacer between the valve stem tip of #2 intake valve and rocker arm pad. Allow tappet to bleed down to give a solid tappet effect.
(8)Install a dial indicator so plunger contacts the #2 intake valve spring retainer as nearly perpendicular as possible. Zero the indicator.
(9) Rotate the engine clockwise until the intake valve has lifted .254mm (0.010 inch).
CAUTION: Do not turn crankshaft any further clockwise as intake valve might bottom and result in serious damage.
(10) Degree wheel should read 3 degrees BTDC to 4 degrees ATDC.
REMOVAL
(1)Disconnect battery.
(2)Drain cooling system. Refer to Cooling System Group 7 for procedure.
(3)Support engine and remove right engine mount.
(4)Raise vehicle on hoist. Drain engine oil.
(5)Remove oil pan and oil pump pick-up. It may necessary to remove transmission inspection cover.
(6)Remove right wheel and inner splash shield.
(7)Remove drive belt. Refer to Cooling System Group 7 for procedure.
(8)Remove A/C compressor and set aside.
(9)Remove A/C compressor mounting bracket.
(10)Remove crankshaft pulley (Fig. 1).
(11)Remove idler pulley from engine bracket.
(12)Remove engine bracket (Fig. 2).
(13)Remove cam sensor from chain case cover (Fig. 3).
(14)Remove chain case cover (Fig. 3).
Fig. 1 Removing Crankshaft Pulley
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Fig. 2. Engine Bracket
(1)Place a scale next to timing chain so that any movement of chain may be measured.
(2)Place a torque wrench and socket on camshaft sprocket attaching bolt and apply torque in direction of crankshaft rotation to take up slack; 41 Nzm (30 ft. lb.) with cylinder head installed or 20 Nzm (15 ft. lb.) with cylinder heads removed. With a torque applied to the camshaft sprocket bolt, crankshaft should not be permitted to move. It may be necessary to block crankshaft to prevent rotation.
(3)Holding a scale even, with dimension reading as shown (Fig. 4), along edge of chain links. Apply torque in the reverse direction to 41 Nzm (30 ft. lbs.) with cylinder heads installed, or 20 Nzm (15 ft. lbs.) with cylinder heads removed. Check amount of chain movement (Fig. 4).
(4)Install a new timing chain, if its movement exceeds 3.175mm (1/8 inch) (Fig. 4).
(5)If chain is not satisfactory, remove camshaft sprocket attaching bolt, and remove timing chain with camshaft sprocket.
(6)Using a suitable puller remove the crankshaft pulley. Be careful not to damage the crankshaft surface.
(7)Position a new crankshaft sprocket on the shaft, install sprocket with suitable tool and mallet. Be sure sprocket is seated into position.
(8)Rotate crankshaft sprocket so the timing mark is to the 12 o'clock position.
(9)Place timing chain around camshaft sprocket and place the timing mark to the 6 o'clock position.
(10)Place timing chain around crankshaft sprocket and install camshaft sprocket into position.
(11)Using straight edge to check alignment of timing marks (Fig. 5).
(12)Install camshaft bolt and washer. Tighten to 47 Nzm (35 ft. lbs.).
Fig. 3 Timing Chain Case Cover
Fig. 4 Measuring Timing Chain Wear and Stretch
(13)Rotate crankshaft 2 revolutions. Timing marks should line up. If timing marks do not line up remove cam sprocket and realign.
(14)Check camshaft endplay. With new thrust plate specification is .0127 to .304 mm (.005 to .012 inches.). Old thrust plate specification is .31 mm (.012 inch.) maximum. If not within these limits install new thrust plate.
(15)Install timing chain snubber. Tighten retaining screws to 12 Nzm (105 in lbs.). These bolts are
20mm long for this model year, they should not be interchanged with previous year engines.
INSTALLATION
(1)Be sure mating surfaces of chain case cover and cylinder block are clean and free from burrs. Crankshaft oil seal must be removed to insure correct oil pump engagement.
(2)Use a new cover gasket, O-rings. (Fig. 6).
(3)Rotate crankshaft so that the oil pump drive flats are vertical.