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'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
1,369 Posts
Discussion Starter #1
Hi everyone,

I replaced the timing chain last week on my V8 M117.985, and the recipe below shows the ingredients used plus the step by step "cheat sheet" which is heavily based on the super effective "how to" YouTube clip
and a guide written by one of my UK colleagues, who's not a member on this forum unfortunately. DISCLAIMER: This is specific to my engine and may not be applicable to your set up, please be mindful of that. Also, this is what worked for me but please don't take this as gospel - use at your own risk.

At any rate I've had 12 degrees retarded which reduced to 10 after replacing the cam sprockets, and to 2 after replacing the chain and tightening everything. To get to 0 I'd have to replace the two sprockets but they cannot be accessed without removing the engine - same goes for additional 2 slides.

The list of components doesn't include valve cover seals or oiler tube clips as they were replaced ca. 300 miles ago. Also, you may want to consider getting new pins (P/N A1160522174, six are needed) for the slide rails especially if your engine is high mileage as the pins may be difficult to remove, and if so can get damaged in the process - I highly recommend getting a pin puller from ebay, cost around USD30 but is a life saver. In hindsight,
the job isn't too much over the top for a DIY as long as you play it safe and take your time as it's quite stressful - you need to be super uber ultra careful not to drop anything into the engine as quite a few threads on this forum teach us. A second pair of hands is useful / recommended for steps 15-40, especially if you're new to this like I was. Thirdly, I posted some pics here in case you want to take a peek - the whole job took 10hours, I think a pro or someone who's been at this before could turn it around in 7 or 8.

Key torque specs:
- Spark plugs and chain tensioner - 25 Nm
- Camshaft sprockets - 100 Nm
- Valve covers - 3 Nm

Part Description Quantity
A0009977694 Chain x1
A116 052 06 01 Cam sprockets x2
N00096101402 Screw x2
A1809900340 Washer x2
N000137014201 Spring Washer x2
A000 997 05 98 Chain Lock Link x1
A117 050 04 15 Tightening Lever x1
A 117 052 08 16 Sliding Rail x1
A117 052 09 16 Sliding Rail x2
A116 050 16 11 Chain Tensioner with gasket x1
N915035000016 Valve cover seal ring copper washers x8
A005 997 77 92 V-belt Power Steering x1
A004 997 85 92 V-belt Alternator x1

1. Disconnect & remove battery - you will be removing the alternator.
2. Remove air cleaner and cover the breather.
3. Label & disconnect plug leads.
4. Remove breather hoses.
5. Loosen drive belt at alternator and PS pump.
6. Remove PS pump and secure upright to the side.
7. Remove the PS pump mounting plate.
8. Remove PS pump mounting plate.
9. Remove spark plugs (not mandatory but easier to turn the engine.
10. Remove alternator and alternator bracket.
11. Removed fan from pulley and remove fan shroud.
12. 27mm socket & short extension on crank nut with a longish ratchet bar.
13. Remove distributor cap.
14. Rotate engine clockwise from front to get to TDC and rotor arm pointing to cylinder 1.
15. Note and mark on the edge of the distributor the position of rotor arm with rotor pointing to cylinder 1 plug and position of distributor relative to head.
16. Remove distributor and PLUG THE HOLE.
17. Use old towel down outside of each valve cover to catch oil.
18. Remove both valve covers.
19. Measure chain stretch by rotating crank clockwise so that right (UK O/S) bank cam mark is aligned with mark on front bearing tower, then read angle on timing marks on crankshaft.
20. Remove chain tensioner from below where alternator usually sits.
21. Replace cam sprockets.
22. Replace guides.
23. Re-fitted distributor so rotor and body still aligned with marks.
24. Pack hole around chain at top of timing case on both banks with cloth to stop anything going down into timing case.
25. Cover cams and as much of valve gear as possible to stop grindings going into engine.
26. Cable tie chain to sprocket in 2 places.
27. Angle grind the heads off two chain rivets between cable ties.
28. Attached new chain to RH end of broken chain with new connector link & circlips
29. Arranged new chain in box so it could feed out easily.
30. Attached a weight via wire to LH end of broken chain and removed cable tie so it hung down the side of the timing case.
31. Rotated crank with wrench clockwise a little to feed new chain onto cam sprocket.
32. Remove outgoing cable tie and add new one so chain is always held onto both sprockets. Do not expect to hold the chain onto the sprockets by hand, with the lumpy resistance from the cam lobes the cam & chain will move suddenly and can come off the sprocket. You could if you wanted remove all the cam followers but this is not a 5 minute job and there is a risk of losing a shim down the engine.
33. Keep adjusting the weight on the old end so it is always tight.
34. Carry on until the old chain is on the floor.
35. Make sure well packed around the timing case holes before removing circlips.
36. Attach 2 new ends to each other with a new link and new circlips.
37. Fill tensioner with oil (optional), fit new gasket and re-attach. Need to hold it towards the block against it鈥檚 strong spring before getting the bolts in to tighten up.
38. Rotate crank to align RH cam mark, read remaining stretch at timing marks.
39. Rotate the engine through several revolutions to check all ok.
40. Refit valve covers with new copper washers.
41. Refit alternator, PS pump, plugs & leads, breather hoses, air cleaner, drive belts (loosely), fan shroud, fan, tighten belts at alternator & PS pump.
42. Reinstall and reconnect battery.
43. START!!!

Best of luck :)

'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
1,369 Posts
Discussion Starter #3
Thanks longbeach1, appreciated - hopefully it will be of value as all V8s need that job, and usually sooner rather than later.

1979 450 SL
1 Posts
I just picked up a 79 450 SL with 212,000 miles and no maintenance history. This is the best thing on the internet today, thanks.

'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
1,369 Posts
Discussion Starter #5
Glad to hear that JD Leonard. In this case you ought to prioritize this job as those plastic slides become brittle with age and heat, and them breaking usually leads to a catastrophic engine failure. Unless they've been replaced recently, which you can judge by the color - mine were original and you can see the dark tea shade on them is a dead giveaway.

R/C107 Moderator
1986 560SL: '84 500SL: '84 280SL 5 speed: other 107s
31,979 Posts
For those that don't know that video is by member PanzerPuff and is also linked in the EGv107 Sticky.

'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
1,369 Posts
Discussion Starter #7
Rowdie, I didn't have a clue that was PanzerPuff... Lol, you learn something every day!

1987 560SL, 2000 Kawasaki W650
961 Posts
I did that job seven years ago on my 560SL already. I suppose at some point I鈥檒l want to do it again. I forget if there鈥檚 an established interval, but I vaguely recall a suggestion of every ten years.

I documented that operation well enough that I can use this site as my repository for the work, with step-by-step photos, including the 鈥渄on鈥檛 do that again鈥 warnings. At least this time I鈥檒l have a nice air-conditioned garage to work in, one of my prerequisites when house-hunting later that year.

I now have a complete set of paper shop manuals鈥攅asier to read IMHO鈥攁nd a Hazard Fraught Tools shop nearby for any use once-and-discard tools

1974 450SL (US), 2005 SLK200 (UK)
317 Posts
Many, many thanks for your detailed and comprehensive post! Much appreciated. Andy

'80 450SLC Afro RHD Ikonengold
2,883 Posts
Great post Miko1aj, along with Panzers video it removes the unknown for those with no professional experience in the industry.

I hope you sorted your starting issues for good as well...

'79 450SL, '04 CLK200 convertible; former A124, W210, A209.
1,369 Posts
Discussion Starter #11
@therling, thanks for linking in your thread - between those topics and EvG I think we've the V8's covered quite well :)
@Andy - you're welcome, I hope it will be helpful on your journey - any questions or concerns just ping.
@DJEnka - thanks, all good with Eleanor. Haven't had any start up hiccups since replacing the thermostat back in January, happy motoring since. The timing change was the last big ticket item before my baby girl goes off for respray in Q4. I hope all is well with your SL too?
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