opic number – GI05.10-P-052324
Date – 12-08-2017
Validity – Engine 651
Complaint
For approx. 2-5 seconds after starting the engine a clattering or pounding noise may be able to be heard from the area of the chain drive.
Note:
The noise of the complaint must be compared with the reference sound sample in the “Sound” attachment!
Soundfile – File hosted by www.w212ownersforum.com
Cause
The timing chain may be stretched. The reason for this may be the chain tensioner.
Remedy
1. Remove chain tensioner (AR05.10-P-7800*).
Note:
Detach rear bracket from air duct housing and detach oil dipstick guide tube at top.
For vehicles with ECO start/stop function:
Remove bolt from starter shield below the chain tensioner, lower shield.
2. Attach measuring chain tensioner W 651 589 11 63 00 without seal 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 on the scale of the measuring chain tensioner according to the vehicle’s driven distance:
Vehicle mileage up to 250,000 km:
Elongation of timing chain less than or equal to 82 mm: Perform work procedure A.
Elongation of timing chain greater than 82 mm: Perform work procedure B.
Vehicle mileage over 250,000 km:
Elongation of timing chain less than or equal to 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-P-7800*).
Work procedure B:
1. Replace timing chain (AR05.10-P-7601*).
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.
2. Check of camshaft sprockets.
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.
Camshaft sprockets with object number A 651 052 00 01 must be replaced (AR05.20-P-6992*).
Notes:
The camshafts do not need to be removed.
The object number is clearly visible on the camshaft sprockets (see picture in attachment).
As of 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-P-7800*).
Note:
Measurement of the elongation of the timing chain must be documented. The documentation is to be sent in together with the removed parts.
The measuring chain tensioner W 651 589 11 63 00 is fitted with an O-ring and a pivoting scale. This makes it easier to read off the elongation.
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* Use the corresponding WIS document.