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BenzMatic 08-01-2003 07:13 PM

W126 Timing chain help
I need help from all the timing chain experts, I think chain skip a tooth. My car is 1987 420sel with 140,000 miles on it and I was doing timing chain rail replacement which went fine. After the chain rails the stretch was 9 degrees, so I decided to roll a new chain. When I was rolling the chain, my vise grip sliped which was holding the chain to cam gear. It did not look like that chain slipped so I proceeded to roll the rest of chain. Once all the chain is rolled, it looks like it is short a link or 2 because I can not put the connecting link together.
My asumption, may be I skip a tooth when vise grip slipped but why is chain short, no idea. If I did skip a tooth, how should I adjust the chain back to specs, should I align the timing marks on both cam gears and crank pully and then try to move chain or what, I am lost. Can use all the help in the world.

Sorry for long post.
Thanks in advance

stevebfl 08-01-2003 07:22 PM

I would remove all the rocker arms to be safe. Then I would push the tentioning rail all the way in. If the chain won't reach put a wrench on each cam gear and try backing them up to find the slack. once the chain is together roll the engine through a number of revolutions and set the crank to TDC. See where your cams are and individually remove the bolt and tap the gear off. Turn the cam to the right position and align the gear by jumping the appropriate number of teeth.

By removing the rockers first you avoid any chance of banging the valves.

BenzMatic 08-02-2003 01:32 AM

Thanks for reply Steve.
I will try this, anybody else has any other suggestions.

Thanks in advance

BenzMatic 08-02-2003 02:36 AM

It seems like I need a special tools to compress the springs to take the rocker arms out, which I do not have. Is there another way of taking the rocker arms out.

MikeTangas 08-03-2003 03:21 AM

On every MB V-8 timing chain I have done, it appears to come up one link short. You have to loosen the tensioner (or remove it completely), this will free up a little slack in the new chain. Remember, the new chain isn't stretched. Of course this means getting the tensioner back in will be a chore, but it is doable.

Youo are installing a new tensioner to go with the new chain, aren't you?

BenzMatic 08-03-2003 06:14 AM

Thanks Mike, that was it. I learned it hard way, I tried to take off the rocker arms as Steve suggested, but did not have the MB valve spring compressor tool. Then I pushed the Tensioner rail all the way in and that freed up enough slack to connect the chain. I double check the timing marks and they all aligned up perfect with ~1 degree stretch.
yes I have changed all the chain rails with the new tensioner, 2 of my chain rails was broken and chain was touching the pivot pins and timing case. I believe I was very lucky that the chain did not slip, but now I am thinking to take off the oil pan to find the broken pieces since i only found half a rail at the botton of timing chain cover. The chain rails seems to have broken long time ago, but I started to hear the morning chain rattle for couple of days ago.

Thanks again

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