- Check the camshaft journals for wear. If the journals are badly worn, replace the camshaft.
- Check the cam lobes for damage. If the lobe is damaged or excessively worn, replace the camshaft.
- Check the cam surface for abnormal wear or damage, and replace if necessary.
- Check each bearing for damage. If the bearing surface is excessively damaged, replace the cylinder head assembly or camshaft bearing cap, as necessary.
Removal & Installation
- Before servicing the vehicle, refer to the Precautions section.
- Disconnect the negative battery cable.
Remove the camshaft (Double VANOS) adjustment unit as follows:
- Remove the intake filter housing with Mass Air Flow (MAF) sensor.
- Remove the fan impeller with fan clutch and cowl.
- Remove the cylinder head covers.
- Remove the spark plugs.
- Remove the plastic cover for intake camshaft.
- Remove the oil pressure pipe.
- Install a special tool, 11-3-450, with banjo bolt on oil pressure connection unit.
- Cover the camshaft adjustment unit.
- Connect a compressed air hose to the special tool fitting on the oil line connection.
- Rotate the engine, a least 2 turns in direction of rotation, to return the camshafts to TDC position (front cam lobes pointing to 10 o-clock and 2 o-clock positions).
- Install a special locking tool, 11-2-300, into hole to lock flywheel in TDC position.
- Remove the 2 studs from the rear of the cylinder head outer edge. Secure the camshafts with locking tools, 11-2-240.
- Disconnect the compressed air hose from the special tool.
- Using care so no oil drips onto belt drive, remove the screw plugs from the camshaft adjustment unit cover corresponding to the forward ends of the camshafts. Have a container to catch oil that runs out.
- Using short, flat nose pliers, remove sealing caps through screw plug openings, then remove the fitting screws (left-hand thread) from both camshaft forward ends.
- Detach the plug connection from the camshaft sensor and solenoid valves on both camshafts.
- Remove the engine lifting eye from the camshaft adjustment unit cover.
Remove nuts and remove the camshaft adjustment unit
WARNINGOnce camshaft adjust unit is removed, DO NOT crank engine. The toothed shaft on the intake side camshaft may slip out of the spline teeth and valves could rest of the piston.
- Remove the cylinder for the chain tensioning piston. Use caution as piston is under spring pressure.
- Press down on the secondary chain tensioner at the top and lock the chain in place with a special tool, 11-3-292.
Remove or disconnect the following:
CAUTIONDO NOT release screws from front ends of either camshaft.
Sensor gear from exhaust camshaft
Studs from between both camshafts
- Release the special locking tool so flywheel is free.
- Lift the timing chain off from end of exhaust camshaft and hold it under tension by lifting it straight up.
Rotate the engine against the normal direction of rotation about 30°, using the crankshaft bolt.
CAUTIONTo prevent the intake camshaft from moving the bearing inserts, remove the camshaft no. 1 bearing cap nuts and remove the bearing cap.
- Install a special tool, 11-2-260, to the cylinder head and install retaining bolts into tool and into spark plug holes for cylinders 1 and 4.
- Turn the eccentric shaft of the special tool to pre-tension the bearing caps. Remove the nuts on all bearing caps.
- Relieve the tension from the eccentric shaft of the special tool and remove the tool.
- Remove the bearing caps and keep in order as removed.
Remove the camshaft. Repeat the process for the other camshaft.
NOTEIf cylinder head is to be removed, remove the complete bearing strip with the bucket tappets. Keep in order of original locations.
Check bearing points of bucket tappets for signs of scoring.
NOTEBearing strips are marked -A- for exhaust side and -E- for intake side.
- Be sure centering dowels are in place on retaining pins at bearing points 2 and 7.
- Install the bearing strips.
Oil all teeth, camshafts, bearings, bearing caps, and friction washers before installation.
CAUTIONBucket tappets expand when not subjected to load by the camshaft and therefore require some time before they can be pushed back down. During a rapid assembly sequence, the -closed- valves may still be open and therefore be in contact with the piston. After assembly, wait at least 30 minutes before cranking the engine back to the TDC position.
Pull up the timing chain and feed in the exhaust camshaft. Position the timing chain onto the end of the exhaust camshaft.
CAUTIONTo prevent damaging valves when fitting camshafts, no pistons should be in TDC position.
- Install the camshafts so the cam tips on the intake and exhaust valves on no. 1 cylinder face each other at about the 10 o-clock and 2 o-clock positions.
- Install the bearing caps (caps are marked from the exhaust side, A1 through A7 for the exhaust side, and E1 through E7 for the intake side).
- Install the special tool, 11-3-260, onto the cylinder head as during removal.
Turn the eccentric shaft to pre-tension the bearing caps. Tighten the bearing cap bolts as follows:
- M6 bolts: 88 inch lbs. (10 Nm).
- M7 bolts: 120 inch lbs. (14 Nm).
- M8 bolts: 15 ft. lbs. (20 Nm).
- Remove the special tool.
- Install camshaft locking tools, 11-3-240 on back end of camshafts. Use an open-end wrench to align camshafts (if necessary, machine wrench head so it does not contact cylinder head) so there is no gap at the locking tools.
- Install the middle locking tool, 11-3-244 so it adjoins other tools and is bolted into spark plug hole.
- Lift the timing chain straight up off the exhaust camshaft and hold it under tension.
- Rotate the engine from 30° BTDC to TDC, in normal direction of rotation.
- Using special tool, 11-2-300, lock flywheel in this position.
- Install sensor gear onto intake camshaft. Install the thrust washer over the sensor gear and torque the gear screw-in pins to 15 ft. lbs. (20 Nm).
Feed the chain wheel onto the timing chain so the arrow on the chain wheel faces the upper edge of the cylinder head.
- Install a special tool, 11-4-220 into the cylinder head in the chain tensioning piston bore and bring tool adjustment screw into contact with the timing chain tensioning rail, but no further at this time.
- Check the arrow mark on the chain wheel and adjust if needed so it still points to upper edge of the cylinder head.
- Install and tighten the retaining screw-in pins in the exhaust chain wheel to 15 ft. lbs. (20 Nm).
- Install the secondary (upper) chain tensioner.
- Position the toothed sleeve into the exhaust camshaft to the toothed gaps are opposed. Secure the toothed shaft. Insert the pin of the toothed shaft into the tooth gaps of the splines on the camshaft and toothed sleeve.
- Push in the toothed shaft on the exhaust camshaft until the elongated holes in the tooth sleeve wheel are centered over the bolt holes.
Place forward chain wheels onto special tool, 116-6-180, and position tooth gap on intake chain wheel as shown as feed on the timing chain.
CAUTIONDO NOT alter position of chain wheels and chain when removing the special tool.
- Remove the special tool and position chain wheels on camshafts, so that tooth spaces oppose each other on intake camshaft.
- Align chain with sprocket wheels so tooth spaces are positioned exactly over each other on intake side.
- Install and secure the toothed shaft into the tooth gaps of the splines of the camshaft and chain wheel. Push in the toothed shaft until about 0.4 inch (1mm) of splines can still be seen.
- Note the installation direction of the corrugated washed so -FRONT- is visible. Install the washer and tighten retaining nuts snug only at this time.
- Install 4 bolts on exhaust side to retain chain wheel. Initially tighten to about 36 inch lbs. (5 Nm), then slack off one-half turn.
- Install the thrust washer over the exhaust side chain wheel.
Note the installation direction of the cup spring (2) so the -F- stamp is forward. If -F- is no longer visible on used engine, install the cup spring so the small locating diameter of the spring points to the sensor gear. Install the cup spring.
- Position the sensor gear over the cup spring so the arrow on the sensor gear is in line with the upper edge of the cylinder head. Install retaining nuts but do not fully tighten.
- Pull out the exhaust side toothed shaft to the stop.
- Press down the secondary chain tensioner at the top and remove the special locking tool.
- Use a special tool, 11-4-200, to preload timing chain tensioning rail by rotating the adjusting screws of the tool with a small wrench.
- Preload the exhaust side cup spring slightly be pressing on the sensor gear and hand-tighten the gear retaining nuts (do not fully tighten yet).
- Remove any remaining gasket material from mating face on front of cylinder head.
- Check dowel sleeves for damage and for correct installation position.
- Make sure sealing face is clean and free of oil.
- Fit special tool, 11-6-150 without gasket over both toothed shafts. Tighten retaining nuts to hold tool in place. Hand-tighten only until special tool is uniformly in contact with cylinder head.
- Insert bolts on exhaust side chain wheel and tighten to about 36 inch lbs. (5 Nm).
- Initially tighten nuts on both exhaust and intake chain wheels to about 36 inch lbs. (5 Nm).
- Torque bolts on exhaust chain wheel to 15 ft. lbs. (20 Nm).
- Torque nuts on exhaust and intake chain wheels screw-in pins to 88 inch lbs. (10 Nm).
- Pull back the special tool from the flywheel.
- Remove the special tools from the rear of the camshafts.
- Crank the engine twice in the direction of rotation until the cam lobe tips on the front of the camshafts point inward at about the 10 o-clock and 2 o-clock positions.
Lock the flywheel with the special tool to the crankshaft is at Top Dead Center (TDC) position.
WARNINGDO NOT turn the engine against normal rotation.
Install the special camshaft locking tool, 11-3-240, onto rear end of camshafts to hold its position.
NOTEThe camshaft timing is correctly set if the special tool rests on the camshafts without a gap on the cylinder head or any protrusion up to 0.04 inch (1mm) on the intake side.
- Remove the special tool from the camshaft forward ends.
Install the camshaft adjustment (Double VANOS) unit as follows:
- Ensure dowel sleeves on forward mating face of cylinder head are not damaged and are correctly installed.
- Keep sealing faces clean and free of oil.
- Apply a thin and even coat of sealing compound, Drei Bond 1209, to contact surface edges of the separating face between the cylinder head and the camshaft adjustment unit.
Install or connect the following:
New seal on mating face
- Set camshaft timing, if necessary.
- Complete installation in reverse of removal procedure.