E300D timing chain stretch - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 06-09-2011, 06:14 PM

With my '96 E300D's engine (W210, OM606NA) now over 277,000 miles, I decided to check for timing chain wear. After pulling the valve cover (a lot more work than the same job in my OM603) I inspected the timing chain, [exhaust] cam sprocket, and the spur gears that transfer motion from the exhaust cam to the intake cam. I could see no visible wear. Pulling up on the chain (as if I were trying to lift it off of the sprocket) produced almost no movement, indicating minimal chain wear.

Next, I turned the crankshaft (27 mm socket and ratchet) towards TDC until I could slip a 6 mm bolt through the holes in the intake cam gear and the first intake cam bearing cap.

When the holes were aligned so that the bolt was a slip fit, I checked the alignment holes on the two camshaft gears. They appeared perfectly aligned, as evidenced by the red line I Photoshopped into the picture.

Finally, I checked the scale on the crankshaft and found that there was almost exactly 1 degree of chain stretch. Since 5º or more is considered "time to change the chain," this means that the chain will likely be good for the life of the engine. Should the chain break some day far down the road, that too is "the life of the engine."

I attribute this longevity to Mercedes' good design and the care that the three POs and I have taken to keep the oil clean. A word to the wise: remember to remove the 6 mm bolt before replacing the valve cover!

Jeremy

engatwork · #2 06-09-2011, 07:49 PM

Good pictures Jeremy.

KarTek · #3 06-09-2011, 08:37 PM

Nice pictorial, thanks!

tarbe · #4 06-09-2011, 09:13 PM

Serious engine porn.

Such clean internals. Beautiful!

Tim

Jeremy5848 · #5 06-09-2011, 09:47 PM

Hey, stop drooling on my nice clean engine!

In other news, the engine is mostly back together. I ran it long enough to be sure the hard line connections didn't leak. Now I can put the intake manifold back and button 'er up.

Seriously, thanks for the compliments.

Jeremy

Zulfiqar · #6 06-09-2011, 09:56 PM

quick question,

Ive got an OM606 also, and it had a removable TDC pointer, in order to service the water pump it needs to be removed, I did the water pump not long ago and had to remove the bracket, I had put some marks on it but were grease pencil marks - and they washed away (because I literally wash everything I open up with solvent) - I tried my best to align it to the worn out depression (scratches) the mounting screw had left on it.

now how can we determine TDC again at this point? i.e. if I would want to check chain wear.. or for any other job that requires TDC to be set.

Zulfiqar · #7 06-09-2011, 10:01 PM

btw what engine oil do you use, the engine is incredibly clean.

Jeremy5848 · #8 06-09-2011, 10:35 PM

The three POs used ordinary dino oil. I switched to Mobil-1 TDT 5W-40 when I got the car at 248,000 in late 2007. The oil and filter were last changed in December 2010 at 273,000.

Now at 277,000, the engine also benefits from the disconnected EGT system, which keeps a lot of soot out of of the intake. Some of that recycled exhaust has to end up in the engine oil if you don't do something about it.

The standard method of setting TDC is to use a dial indicator on the #1 piston top but that means pulling both the injector and the prechamber. Maybe someone else will suggest an easier way.

If that isn't possible, you can use the screw-in-the-hole method of setting the cams where they are supposed to be at TDC and then adjusting the pointer until it reads (in degrees) what you know to be the chain stretch (because you wrote it down before taking the pointer off).

If you didn't do that, you can just set the pointer to TDC when the cams are lined up and remember that it may not be exactly TDC. You can use that as a reference for future work.

Jeremy

Zulfiqar · #9 06-09-2011, 10:43 PM

I'll adjust it when I take the valve cover off for any work.

Skid Row Joe · #10 06-10-2011, 12:26 AM

Great stuff, Jeremy!

I thank you, and my '99 300 ETD thanks you!

michakaveli · #11 06-13-2011, 04:14 PM

Cool thread. Thanks for posting!

Diesel911 · #12 06-13-2011, 07:20 PM

Quote:

Originally Posted by Zulfiqar

quick question,

Ive got an OM606 also, and it had a removable TDC pointer, in order to service the water pump it needs to be removed, I did the water pump not long ago and had to remove the bracket, I had put some marks on it but were grease pencil marks - and they washed away (because I literally wash everything I open up with solvent) - I tried my best to align it to the worn out depression (scratches) the mounting screw had left on it.

now how can we determine TDC again at this point? i.e. if I would want to check chain wear.. or for any other job that requires TDC to be set.

For a 617.952 the service manual shows removing the Prechamber on #1 and gatting a Dial Indicator extension pointer down on the top of the Piston Head to find TDC (with this method any stroke is OK).

ARMY had the ides of getting the Piston up near TDC, Removing a Valve Spring and letting a Valve drop onto the head of the Piston. The Valve now becomes the Extension for the Dial Indicator.
The catch is that the 617 Engines use Nuts instead of Valve Stem Keepers to hold the Spring Retainer on. On the newer Engine it may not resonably be possible to To loosen a Valve while it is on the Engine without disturbing other stuff.

Maxbumpo · #13 06-14-2011, 08:33 AM

Very nice tutorial, I've just one addition. I used the same method (6mm bolt) and found that it allowed too much movement of the cam shaft gear, so I could get readings over a range from 1 to 4 degrees.

Quote:

Originally Posted by Jeremy5848

Next, I turned the crankshaft (27 mm socket and ratchet) towards TDC until I could slip a 6 mm bolt through the holes in the intake cam gear and the first intake cam bearing cap.

After a bit of research, I learned that the hole is 6.75mm diameter, so a more accurate reading of the chain stretch is possible if you use the Mercedes special tool (see FSM procedure 05-6010HA, tool is 111 589 03 15 00) or make your own. I think that a 6.5mm drill bit would also be an improvement.

Rafi · #14 06-14-2011, 09:22 AM

high quality pics, should not be watched without pants.

Oldwolf · #15 06-14-2011, 09:58 AM

I know my 602 is not the same as your 606 but is the process the same for checking chain stretch?