Engine noise (rattling) after engine start
Topic number

LI05.10-N-057796

Version

3

Design group

05.10 Timing chain drive, toothed belt drive

Date

07-21-2016

Validity

ENGINE 651 in model 900, 906, 636, 639

Reason for change

Part numbers updated and operation number for "Test +
work procedure B (camshaft sprockets are replaced)" adjusted

Reason for block

Complaint:

Engine noise (rattling) after engine start.
Note:
The noises can be heard approx. 2-5 seconds after engine start. Rattling or knocking noises can be heard in the area
of the chain drive.
Note:
The noise of the complaint must be compared with the reference sound sample in the "Sound" attachment!

Attachments
File

Description

KTS OM651.MP3.mp3

Problem noise.
Note: The area (6) shown in the video is to be checked
acoustically for approx. 10 seconds.

Cause:

The timing chain may be stretched. The reason for this may be the chain tensioner.

Remedy:

1. Remove chain tensioner (AR05.10-D-7800WE, AR05.10-S-7800SJ).
2. Install measuring chain tensioner W 651 589 09 63 00 without sealing ring and tighten to 20 Nm.
3. Crank engine 2x and set 1st cylinder to ignition TDC. While doing so, determine the highest display value for the
measuring chain tensioner throughout the entire procedure. This is generally found at ignition TDC for cylinder 1.
4. Evaluate the value read off the scale of the measuring chain tensioner:
Elongation of timing chain less than 84 mm: Perform work procedure A.
Elongation of timing chain greater than 84 mm: Perform work procedure B.
Work procedure A:
1. Install new chain tensioner (AR05.10-D-7800WE, AR05.10-S-7800SJ).
Work procedure B:
1. Replace timing chain (AR05.10-D-7601WE, AR05.10-S-7601SJ).
Note:
Depending on the degree of chain elongation, swirl marks may be found on the cylinder head. These are inconsequential and they do not justify a replacement of the cylinder head.
07-21-2016 3:48 PM
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2. Check of camshaft sprockets.
Camshaft sprockets with the object number A 651 052 00 01 are to be replaced by A 651 052 00 00 (AR05.20D-6992-08WE).
The camshafts must be removed in order to replace the camshaft sprockets.
•
Model 639: AR05.20-S-6992SJ
•
Model 906: AR05.20-D-6992WE
Camshaft sprockets with object number A 651 052 00 00 may only be replaced if they are seriously worn (pitting, broken tooth tips). An intact sprocket has a uniformly polished surface at the chain inlet; this is not grounds for replacement.
Note:
The object number is clearly visible on the camshaft sprockets (see picture in attachment).
As of production month 03/2012 the engines are fitted with the camshaft sprockets with object number A 651 052 00
00 as standard.
3. Install new chain tensioner (AR05.10-D-7800WE, AR05.10-S-7800SJ).
Note:
The measurements of the timing chain stretch must be recorded on the workshop order.
If the damaged parts are to be returned, the measurements must also be documented on the parts return note.

Attachments
File

Description

01.jpg

Part number of camshaft sprocket.

Symptoms
Power generation / Engine noise / Chattering
Power generation / Engine noise / Clanking
Power generation / Engine noise / Rattling
Power generation / Engine noise / Clattering
Power generation / Engine noise / Pounding

Parts
Part number

ES1 ES2 Designation

Quantity Note

EPC

A 651 052 00 00

Camshaft sprocket

2

Improved steel wheels

X

A 651 050 08 00

Chain tensioner

1

Modified chain tensioner

X

A 000 993 82 76

Timing chain

1

X

Operation numbers/damage codes
Op. no.

Operation text

Time

Damage
code

Note

05131 36

Chain tensioner noise

05-7800

REMOVE/INSTALL CHAIN TENSIONER, REPLACE IF NECESSARY

Test + work procedure A

05-0000

CHECK LENGTH OF CHAIN (CHAIN
TENSIONER REMOVED)

Test + work procedure A

05-0000

CHECK LENGTH OF CHAIN (CHAIN
TENSIONER REMOVED)

"Test + work procedure B

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(camshaft sprockets are not replaced)"
01-5014

REMOVE/INSTALL/SEAL CYLINDER
HEAD COVER (1)

"Test + work procedure B
(camshaft sprockets are not replaced)"

08-7601

REPLACE TIMING CHAIN (CYLINDER
HEAD COVER REMOVED)

"Test + work procedure B
(camshaft sprockets are not replaced)"

05-0000

CHECK LENGTH OF CHAIN (CHAIN
TENSIONER REMOVED)

"Test + work procedure B
(camshaft sprockets are replaced)"

01-5014

REMOVE/INSTALL/SEAL CYLINDER
HEAD COVER (1)

"Test + work procedure B
(camshaft sprockets are replaced)"

05-0000

REPLACE TIMING CHAIN (CAMSHAFTS (ALL) REMOVED)

"Test + work procedure B
(camshaft sprockets are replaced)"

05-6992

REMOVE/INSTALL CAMSHAFTS (ALL)
(CYLINDER HEAD COVER REMOVED)

"Test + work procedure B
(camshaft sprockets are replaced)"

05-0000

REMOVE/INSTALL CAMSHAFT
SPROCKETS (ALL), REPLACE IF NECESSARY (TIMING CHAIN REMOVED)

"Test + work procedure B
(camshaft sprockets are replaced)"

Attachments
01.jpg:

07-21-2016 3:48 PM
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