Hi all. I just got done replacing the first of my two OM642 timing chains. Many thanks to the contributors on this forum!
The instructions in WIS show a slightly different tool than what is being sold for mercedes timing chains though. And the dirty little secret is that you need to remove and reinstall the intake cam in order to use the tool. This is because the chinese tool doesn't account for the drive gear blocking access to the rear of the chain.
The instructions in WIS show the new link being pressed in from the rear, and then the final endplate being pressed on from the front. This gives access to do the final crimps from the front,
Knockoff tools don't account for the OM642 exhaust camshaft drive gear, which means that you either need to remove and reinstall the intake cam several times, or hack something like the youtube videos showing the guy beating on the camshaft with a hammer. Not gonna do that!
The chinese tools for multiple mercedes engines are available pretty cheap on ebay. But I bought a pretty expensive one from Taiwan (IDParts) that claimed to be specialized for OM642. And I was hoping that it would provide for the OM642 cam drive gear. Sadly though... it does not.
Some folks complained about the quality of the steel in the cheap chinese tools. The taiwanese tool from IDParts seems to be of generally good quality with nice hard steel parts. But it is definitely not designed to work around the OM642 camshaft drive gear. So I modified it.
Here's how it works.
Chain Breaker:
To break the old chain, the link-pin should be pressed out from the rear towards the front. To do this, you need a notch cut in the frame of the breaker tool to make the inner width at least 36mm. The notch needs to be at least 6mm deep. See pictures.
My expensive taiwanese tool has a long enough pin that I could push the link-pin all the way out with just the fine-thread inner screw and didn't need to advance the outer coarse-threaded. If yours is not that long, it might be necessary to also grind down the end of your coarse-thread screw to clear the gear. In that case, I would probably advance the coarse-thread screw just as far as necessary and then grind a flat on it, rather than trying to reduce the entire outer diameter of the screw.




Press-tool:
The press tool also needs to be widened, but opposite the threaded end. You'll press the new link from the rear towards the front. Then change bits, turn the tool around and press on the end-plate on from the front. Then crimp from the front.
Cut a notch in the tool to make the total inside width at least 65mm. The notch should be about 7mm deep. This will leave enough support for the tool that bears up against it but clear the gear.



Bits:- Two of the interchangeable bits need modification.
1- The bit that presses the new link into the chain needs to be cut off just below the pin recesses. This tool is driving the link by the ends of the pins, not pressing on the side plate, so as long as you leave the recesses intact, it'll be fine. In WIS, look closely at the pictures of the tool and you'll see the factory tool is like that. I cut a little more off of mine than necessary and could easily have left another 1 or 2mm below the recesses and it still would have cleared the gear. Be careful pressing the link in, to make sure that the new link doesn't get hung up on the edge of the gear. You may need to lift the tool slightly at that stage to help the link up over the edge of the gear.
2- The backer piece that is used while pressing on the end-plate and also while doing the final crimp needs to have the ridge ground flush toward the ends of the channel. Here's the problem: that backer piece is wide enough for the channel to engage four pins (the two new-link pins plus the two adjacent pins in the chain). If the chain is laid out flat, this piece will work fine, but if we want to use it with the chain wrapped around a gear, the pins in the adjacent links will not line up with that channel. So grind the area toward the ends flush so the adjacent pins don't need to line up with the channel. When you're doing the final crimp, you'll need to lean the tool a bit so that the adjacent pin lines up with that channel.


Hopefully this saves someone from having to remove their intake cam... or beat up on it with hammer...