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So at 54,600 miles I started getting a terrible rattle at startup. Checked into it and appears that some of these OM642 engines develop stretched timing chains. I'm a pretty good mechanic, don't really have time for this sort of thing because I'm busy, but we have a third car, so what the hell. Ordered up the parts and some of the special tools, then dove in.
You have to remove a hell of a lot of stuff to get to this thing. I removed both valve covers because I started to get paranoid about "how do I confirm the timing is correct if I can't see both sets of cams?" Probably went overboard on that, I admit.
That's a lot of parts that have to come off.
Anyway, the old chain was definitely badly stretched, so it's not a wasted effort. It's off and headed to the scrap heap.
Headed to the scrap heap to be recycled.
So now I'm at the point where I have the new chain in, and I go to use the tool that I bought which is supposed to be an exact copy of the MB Factory tool, to install the last link in the chain. There are three steps to this process (I'll do an entire write up once I'm finished and confirmed that I did it correctly ) First, you install the center link and hold it in place with a small fixture that looks like a chain link with pins. Then you insert the new link pins and use a tool to press that center link through the pins on the new link. Second you press on the end link, and last, you crimp ("rivet" in MB speak) the pins to keep the end link from falling off.
In the WIS, they show that you do this with the chain resting on the sprocket of the intake camshaft on the passenger (USA) side (the "Right" side in MB speak.) But the tool won't let me do this because the gear on the cam that is only millimeters from the sprocket, is interfering with the tool and not allowing me to have the tool level. I'm certain that if I try and press it this way, that it's not going to work, so I backed off and figured I'd seek some guidance before I screw up the hard work I've done to get to this point.
Anyway, here is where I am in the process (i.e. trying to get the center link pressed through.)
Connecting the new chain with a new link.
My question is this: I bought the tool pictured below. I'm wondering if there is a set of inserts (the small blocks and elbow shaped things in the top of the case) that is specific to the OM642 that did not come with my kit, and do I need to buy that specific set? That's because the WIS is showing the chain riveted at the point where I am now, but this tool is not fitting. My thinking was that perhaps if I had a set of blocks that were a little thicker it would get me the few millimeters of clearance that I need to rivet this chain and get this thing back together. Does anybody know?
I am watching your timing chain post with baited breath excitement! Mine has already been done by since its the same engine as my car and I discussed this at such length with the dealer I take great interest in it.
On your question regarding the rivet tool, would you ever separate the cam sprocket from the cam for just the rivet operation, then reinstall that cam?
Was it hard to feed the new chain through?
What the heck are those alternate color links on the old timing chain? How much had it stretched? Mine had stretched 12mm.
"On your question regarding the rivet tool, would you ever separate the cam sprocket from the cam for just the rivet operation, then reinstall that cam?"
Krusty, yes, that would be an option...except...there are three bolts that hold the sprocket onto the camshaft. I only installed two of them when pulling the chain through. Mercedes made no provision for removing the bolts if they are below the head...and one of them is below the head right now. I'm used to working on BMW's...and BMW installs plugs so that you can remove the cam sprocket if the bolts are in that position...so this is just one of many engineering decisions by Mercedes that I'm very unimpressed with.
At this point I'm pretty limited in my choices. One of them is to take a grinder to my new tool....the other is to find another tool or set of inserts that works with this one. There are probably other options, but I'm not seeing them at the moment.
"On your question regarding the rivet tool, would you ever separate the cam sprocket from the cam for just the rivet operation, then reinstall that cam?"
Krusty, yes, that would be an option...except...there are three bolts that hold the sprocket onto the camshaft. I only installed two of them when pulling the chain through. Mercedes made no provision for removing the bolts if they are below the head...and one of them is below the head right now. I'm used to working on BMW's...and BMW installs plugs so that you can remove the cam sprocket if the bolts are in that position...so this is just one of many engineering decisions by Mercedes that I'm very unimpressed with.
At this point I'm pretty limited in my choices. One of them is to take a grinder to my new tool....the other is to find another tool or set of inserts that works with this one. There are probably other options, but I'm not seeing them at the moment.
hey man, any update on this ? I have the GL350 with 49k on the clock and it sends a shiver down my spine everytime I hear about stretched timing chains...
Not sure, but from the photos it looks like the the cam shaft is free, so an option you potentially have is to remove the cam with the pulley and phaser assembly, remove the phaser assembly from the cam, connect the chain link, install cam, install phaser/pulley assembly under the now-connected chain, put in two bolts, turn the motor over to get the third bolt in.
I have a couple options that I've thought of in the last day or two:
1. Reinstall temporary link, rotate engine and remove the bolts on the sprocket, allowing me to remove it and then rivet the chain.
2. As stated above, pull the cam again and rivet the chain.
3. Modify the tool somehow, and rivet the chain in place where it is.
I got some time last night to look at it again and I've decided on #3. Basically I just need to shim the inserts to raise them up about 3 mm, and add a spacer to the bolt side which will let me raise the anvil. I should be able to get that done today over lunch and maybe can get this resolved quickly.
I'm very hesitant to pull the cam again, it's a recipe for messing up the timing without the hold-down tools, and my helper won't be around for a while so I want to take the path of least resistance.
homeyclaus, that looks like good times. BTDT in the race track paddock on too many occasions.
Worked from home today and fabricated the first insert over lunch. I now have the new link pressed in.
The tool was aligned properly at this point, so pressing the link in was academic.
Fabricated this insert for the factory tool, and raised up the die by using some neodymium magnets.
Now I need to fabricate up something similar for pressing on the end link and crimping the pins. That will take a little longer than the 30 minutes that this took.
The chain is now riveted and the timing has been confirmed good. Those betting that the camshaft had to come back out should pat yourselves on the back. I rotated the chain until the link was just shy of appearing and removed the bolt from the sprocket. Then I turned it until the new link was front and center, removed the can (after setting it on the timing marks) and did the riveting. Now I have to put it back together and write it up for those that want to try it. Given my schedule, that will be the following week at best.
One of the reasons I got a Mercedes this time was because the timing chain replacement procedure was the least onerous by far.
VW has their timing chains at the back of the engine, so you have to pull it to fix it. Google Audi 4.2L timing chain sometime for what that looks like. Then look under the hood of an Audi A8.
The chain is now riveted and the timing has been confirmed good. Those betting that the camshaft had to come back out should pat yourselves on the back. I rotated the chain until the link was just shy of appearing and removed the bolt from the sprocket. Then I turned it until the new link was front and center, removed the can (after setting it on the timing marks) and did the riveting. Now I have to put it back together and write it up for those that want to try it. Given my schedule, that will be the following week at best.
Excellent work bro! .. Excuse my lack of knowledge, how do you verify timing is good ? (something to do when cyl 1 is TDC ?)
I'll go over this in detail when I do the write up, but look in the photo above and you will see two yellow dots at the point where the two gears mesh. Each gear has two dots cast into it, 180 degrees apart. They are not colored, but to make them easier to see I filled them with a yellow grease pencil. On each gear, one dot is on a "peak" and the other is in a "valley" and when the gears mesh up, like the photo, a "peak" will always mesh with a "valley." If you pull the camshaft and say "oh no, how do I align the camshaft when I reinstall it because I forgot to mark both of them" you don't have to worry, you align the corresponding dot according to the instructions above. If you align them and find a valley with a valley or a peak with a peak, you know that you have to rotate the camshaft 180 degrees.
Additionally, there are degree marks on the crankshaft pulley, and when you have the #1 cylinder at Top Dead Center ("TDC") then the dots on both sets of cams (right and left cylinder banks) will be aligned, AND the arrow on the timing cover will be pointing at the 360 degree mark.
Update: Buttoned everything up this morning. I didn't expect it to start on the first crank, since the fuel pump has to work fuel into the rails, and wasn't wrong. Apparently I should have disconnected the battery, however, because it was near dead from sitting so long. After I charged it up, is started up this morning on the second try. Drove it to work; no issues.
I'll get a write up done this week sometime for those chomping at the bit to do their own.
Great job Sak,
Did you replace the tensioner as well?
My GL was smoother than new it seemed with new timing chain. I am at 107k miles now and still sounds good so let's hope original chains were bad in this range of engines and not something else.
Yes, replaced the tensioner as well, it came in the kit. The car feels like it did when I got it at 19k, though that was not that long ago...
Funny, posted it on Facebook that I was finally done and a buddy who has a 2011 responded that his is at the dealership right now getting a new timing chain, at 77k. Dealer quoted him $4600 but was covering 1/2. What a crock that MB think they don't have a problem with this engine.
Yes, replaced the tensioner as well, it came in the kit. The car feels like it did when I got it at 19k, though that was not that long ago...
Funny, posted it on Facebook that I was finally done and a buddy who has a 2011 responded that his is at the dealership right now getting a new timing chain, at 77k. Dealer quoted him $4600 but was covering 1/2. What a crock that MB think they don't have a problem with this engine.
I agree with leaving owners hanging on this timing chain issue, really bad business. What I find crazy is I am on the Sprinter forum daily as I have had three of these as well and there is no timing chain issues on OM642s in sprinters, even oil cooler O-rings are nearly unheard of. What do they do differently for the passenger car/suv versions? There is no way that timing chain should stretch 12-13mm in 50k miles.
I agree with leaving owners hanging on this timing chain issue, really bad business. What I find crazy is I am on the Sprinter forum daily as I have had three of these as well and there is no timing chain issues on OM642s in sprinters, even oil cooler O-rings are nearly unheard of. What do they do differently for the passenger car/suv versions? There is no way that timing chain should stretch 12-13mm in 50k miles.
Do you guys think its the tensioner out of spec causing the chain to stretch ? If not what is it ? Crankshaft isn't putting out 1000 HP!!!!!!!!!!
I've read speculation that not enough oil flows to the tensioner, and that results in insufficient tension on the chain. I have no idea if that's what is causing it.
He, well done! BWT, do you mind sharing the tool/method you used to pull out the injectors. I have one that is on the list to do due to a leak so I am now gathering info in the best way to get it out. thx!
The tool that I bought to pull the injectors is made by Schley Products and is their part number 12200. It's called VW/Audi Diesel Injector Puller. I think it was around $85 on either Amazon or eBay.
Thank you Sak.., for sharing the tool you used. My previous research on this topic was showing that not all tools fit/work quite good for this type of injectors, hence me asking.
Does anyone here know if timing chain is covered under the Extended Emissions Warranty? my car has timing chain rattle during a cold start, I do not hear this rattle for rest of the day.
2014 GL350 with 59k miles.
this link shows the new Extended Emissions warranty covers the "Engine Timing Chain".
02-20-2017, 02:36 PM
) First, you install the center link and hold it in place with a small fixture that looks like a chain link with pins. Then you insert the new link pins and use a tool to press that center link through the pins on the new link. Second you press on the end link, and last, you crimp ("rivet" in MB speak) the pins to keep the end link from falling off.
