Timing Chain: Service and Repair
Camshafts and hydraulic chain tensioner, removing and installing
^ Cylinder head installed
Special tools, testers and auxiliary items
^ Counter-hold tool 3036
^ Retainer for chain tensioner 3366
Puller T40001
Removing
- Remove ribbed belt and tensioning element for ribbed belt.
- Remove engine cover panel above cylinder head.
- Remove toothed belt guard (upper section).
- Set crankshaft to markings for TDC of No. 1 cylinder (arrows) by turning central bolt on crankshaft sprocket in direction of rotation.
- Remove cylinder head cover.
- Screw M5 x 55 stud -1- into toothed belt tensioning element.
- Screw hex nut -2- onto stud -1- using large washer -3-.
- Only tension piston of tensioning element as far as necessary to secure it with a locking pin (e. g. from lifting appliance 2024 A) arrow-.
Note:
If it is not possible to insert the locking pin, carefully tension the pressure piston of the tensioning element just enough to allow the toothed belt to be removed.
- Take toothed belt off camshaft sprocket.
- Loosen camshaft sprocket (using 3036).
- Remove camshaft sprocket using puller T40001.
- Remove CMP sensor housing.
- Remove rotor for CMP sensor.
- Secure hydraulic chain tensioner with retainer for chain tensioner 3366.
Note:
If the retainer for chain tensioner is tightened excessively, this can damage the hydraulic chain tensioner.
- Recheck TDC position of camshafts.
Marks on camshafts must be in line with arrows on bearing caps.
- Clean chain and camshaft sprockets opposite two arrows on bearing caps and mark installation position with colored marks.
^ The distance between the two arrows (and thus between the colored markings) is 16 rollers on the chain.
^ The notch on the exhaust camshaft is offset slightly toward the inside in relation to chain roller -1-.
Note:
Do not mark chain with a center punch or by making a notch or similar.
- First remove bearing caps 3 and 5 on intake and exhaust camshafts.
- Remove double bearing cap.
- Remove both bearing caps next to intake and exhaust camshaft chain sprockets.
- Remove securing bolts of hydraulic chain tensioner.
- Loosen bearing caps 2 and 4 of intake and exhaust camshafts alternately and diagonally, and remove.
- Remove intake and exhaust camshafts with hydraulic chain tensioner.
Installing
- Replace rubber/metal gasket for hydraulic chain tensioner and apply a thin coat of sealant D 454 300 A2 to shaded area.
- Install drive chain on camshaft sprockets as follows:
- When the old chain is being re-installed, Install the chain so that the colored markings are in line (arrows).
^ When a new chain is being installed, the distance between the notches -A- and -B- on the camshafts must be 16 rollers on the chain. The illustration shows the exact positions of the 1st and 16th rollers on the sprockets.
^ Notch -A- is offset slightly toward the inside in relation to chain roller -1-.
- Insert hydraulic chain tensioner into chain.
- Locate camshafts together with chain and hydraulic chain tensioner on cylinder head.
- Oil running surfaces of both camshafts.
Note:
^ Dowel sleeves for bearing caps and hydraulic chain tensioner must be located in cylinder head.
^ When installing bearing caps ensure that the identification mark is readable from the intake side of cylinder head.
- Tighten mountings of hydraulic chain tensioner (watch position of dowel sleeves).
- Tighten bearing caps 2 and 4 of intake and exhaust camshafts in stages and in diagonal sequence (watch position of dowel sleeves).
- Install bearing caps next to chain sprockets on intake and exhaust camshafts.
- Check correct setting of camshafts:
^ The two markings on the camshafts must be in line with the two arrows on the bearing caps (arrows).
^ The distance between the two arrows on the bearing caps (or between the colored markings) is 16 rollers on the chain.
^ The notch on the exhaust camshaft is offset slightly toward the inside in relation to chain roller -1-.
- Remove holder for chain tensioner 3366.
- Apply a thin coat of sealant D 454 300 A2 to shaded area on double bearing cap and install bearing cap (watch position of dowel sleeves).
- Install remaining bearing caps (watch position of dowel sleeves).
- Install new intake and exhaust camshaft oil seals.
- Install camshaft sprocket.
Check installation position: Narrow web of camshaft sprocket faces outward (arrows) and marking for No. 1 cylinder TDC is visible from front.
- Install securing bolt for camshaft sprocket (hold in place with retainer 3036).
- Install camshaft position sensor.
- Install cylinder head cover.
- Align camshaft sprocket mark with marking on cylinder head cover.
- Align marking on vibration damper with marking on lower part of toothed belt guard.
Note:
The crankshaft must not be at TDC when the camshaft is rotated, otherwise valves can contact pistons and cause damage.
- Install toothed belt (adjust valve timing).
- Install ribbed belt and ribbed belt tensioning element.
Note:
^ Follow all instructions for removing and installing toothed belt.
^ Wait about 30 minutes after installing the camshafts before starting the engine. The hydraulic valve compensating elements must settle (otherwise the valves will strike the pistons).
^ After working on the valve gear, turn the engine carefully at least 2 rotations to ensure that none of the valves make contact when the starter is operated.