Guide and Tensioning Rails

WM 154719 Removing and installing guide and tensioning rails on 4.8 liter DFI engines

Preliminary work

Preliminary work

1. Remove timing chain.

Information

Component overview

Timing chain and chain guide

1 - Threaded peg
2 - Threaded pegs
3 - Guide rail
4 - Tensioning rail
5 - Chain tensioner with sealing ring
6 - Pin (for locking the oil pump tensioning rail)
A - Direction of travel

Replacing guide and tensioning rails

Removing guide and tensioning rails

Information:
If the timing chain has to be removed or replaced, check the guide and tensioning rails as well as the chain pinions for wear and scoring and replace them if necessary.

Information:
The rolling direction of the timing chain must always be the same.
If the timing chain is to be reused, the rolling direction of the timing chain must be marked before it is removed.

1. If you have not already done so, remove upper guide rails (guide pad) between the camshafts -6-.

Timing chain and sprockets

1 - Double-chain camshaft drive
2 - Camshaft sprocket
3 - Screw, M12 x 140 Tighten completely after setting timing.
4 - Deflector rail
5 - Screw, M8 x 35
6 - Camshaft-to-camshaft guide pad
A - Direction of travel

2. Detach tensioning rail from the threaded peg. -4-

Timing chain and chain guide

1 - Threaded peg
2 - Threaded pegs
3 - Guide rail
4 - Tensioning rail
5 - Chain tensioner with sealing ring
6 - Pin (for locking the oil-pump tensioning rail)
A - Direction of travel

3. Carefully slacken the lower tensioning rail for the oil pump chain.

Press the tensioning rail back with a small screwdriver until both staking holes between the tensioning rail and guide rail are aligned.

Oil pump tensioning rail

4. Stake tensioning rail for oil pump chain through the hole in the guide rail using a suitable drill bit, drift punch or nail. This slackens the oil pump chain.

Staking tensioning rail for oil pump chain

5. Remove guide rail -3-. Tensioning rail for oil pump chain is locked with -6-.

Guide rail

6. Remove deflector rail -4- by undoing the fastening screws -5-.

Timing chain and sprockets

1 - Double-chain camshaft drive
2 - Camshaft sprocket
3 - Screw, M12 x 140 Tighten completely after setting timing.
4 - Deflector rail
5 - Screw, M8 x 35
6 - Camshaft-to-camshaft guide pad
A - Direction of travel

Installing guide and tensioning rails

Installing guide and tensioning rails

1. Fit deflector rail -4- by fitting the fastening screws -5-.

Timing chain and sprockets

1 - Double-chain camshaft drive
2 - Camshaft sprocket
3 - Screw, M12 x 140 Tighten completely after setting timing.
4 - Deflector rail
5 - Screw, M8 x 35 - Tightening torque: 32 Nm (24 ftlb.)
6 - Camshaft-to-camshaft guide pad
A - Direction of travel

2. Fit guide rail -3-. Small tensioning rail is locked with -6- at the guide rail. Slide guide rail onto the threaded pegs and move into the correct installation position with respect to the fitted drive chain for the oil pump. Pull locking pin (this brings the tensioning rail in contact).

Guide rail

3. Slide tensioning rail onto threaded peg. -4-

Timing chain and chain guide

1 - Threaded peg
2 - Threaded pegs
3 - Guide rail
4 - Tensioning rail
5 - Chain tensioner with sealing ring
6 - Pin (for locking the oil-pump tensioning rail)
A - Direction of travel

Information:
The rolling direction of the timing chain must always be the same.
If the timing chain is to be reused, the rolling direction of the timing chain must be marked before it is removed.

4. If you have not already done so, fit upper guide rails (guide pad) between the camshafts -6-.

Timing chain and sprockets

1 - Double-chain camshaft drive
2 - Camshaft sprocket
3 - Screw, M12 x 140 Tighten completely after setting timing.
4 - Deflector rail
5 - Screw, M8 x 35
6 - Camshaft-to-camshaft guide pad
A - Direction of travel

Subsequent work

Subsequent work

1. Install timing chain.
2. Install timing-case cover.
3. Set the timing.