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Old 08-14-2003, 07:48 PM
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OM603 timing chain installation report

Sent this to the MBZ.org and Stu Ritter lists, thought I'd add it here for the archives as well...

One note is that while the 617 sprocket is fully exposed with the valve cover off, the OM60x sprocket is 2/3 hidden by the cylinder head, only the top 1/3 protrudes. So those of you comparing to 617 jobs, keep that in mind!




==========
Hi all,

Well, I tackled the timing chain in my 1987 300D this past weekend. I slowly accumulated the proper tools over the last ~2 years (long story, see separate post) which ended up paying off, sort of. Some background info first. I bought the car with 186kmi on the odo, and assume it was fed dino most of its life. I switched to Mobil-1 pronto with no ill effects, consumption is about 7kmi per quart. While replacing the cylinder head in spring 2002, I adjusted the TDC pointer with a micrometer on the piston crown (it was off one degree). Then I checked chain stretch with the eyeball method numerous times, and compared to the dial gauge method on the valve lifter. The numbers matched - 4 degrees stretch, the limit at which MB dictates a new chain is in order. Way back in '02 when I got the chain it was a measly $55, the price has gone up significantly since then. It was an Iwis (OEM) chain. It sat in my shop, rather lonely and ignored, for the past 18 months or so. Now let's fast forward to last weekend.

First I double-checked the chain stretch, yep, still at 4 degrees. Checked IP timing and it was 13.5-14.0, where I had set it previously. After covering up the chain cavity & cam, I took my now-huge-looking 5-inch angle grinder to a link on the old chain. Yeeesh, I wish I had something smaller, it was like swatting mosquitoes with a sledgehammer. Anyway I finally ground enough off the ends and discovered those plates are really STUCK on there! Pliers coaxed it off. I had installed the chain loader (retainer), but as you are about to learn, I did not have it tight enough against the sprockets. I used a clip-type master link to attach the new chain to the old, and started slowly cranking away. Then disaster struck. About 10 links in, I noticed the crank (which I was turning by hand), was moving forward while the chain was not! Oh SH...OOOT! Not good. It was already 90 degrees but my sweat output about tripled at that point. I saw the retainer was allowing the chain to pull off the sprockets on the feed side! Aaaagh! I hoped it would let me still turn the engine, but I could tell with one more partial turn that pistons were kissing valves - very positive stop.

So, I sat down in my pool of perspiration and felt faint for a while. Now what? I tried turning just the cam forward, no go - wouldn't budge (odd). By a total fluke, the crank happened to be right on TDC - I had made one full turn so far. I decided to pull the cam, set it on TDC, so at least the cam & crank would be in time. A little more thinking and I decided hey, while I was at it, I could turn the crank 1 turn with the cam out, and get it back in time pretty close. I knew the IP was likely out and would require an R&R to remedy, but that was to be a later headache. Problem now is, the factory manual specifies how to pull the cam when it's at TDC- not 180 degrees out! Different lobes are under tension, and following the factory sequence could mean a snapped cam. More perspiration (d'oh!). Oh well, worst case I get a new cam out of the deal. I did every other cam tower bolt, one turn, in a Z-shaped pattern back & forth, slowly letting the cam up. Thankfully it survived. I turned the crank one more turn, keeping TIGHT rein on the feed side of the chain... The IP piston tension likes to periodically YANK the chain in and you really have to pull hard to keep it out, otherwise the IP will get out of time (BT, DT on the head job last year - wasn't fun).

OK, turned the crank back to TDC again, re-installed the cam at TDC, then re-installed the now modified chain loader. (I beat on it to bend the edges in so it was TIGHT on the sprocket this time.) I slowly rolled the chain the rest of the way in, and when it was done, I had one extra link! Greeaat. I figured that was the slack side for the tensioner and "dropped" the extra link down, ignoring that little quirk for now. I installed the clip link on the new chain and turned 2 more turns to make sure nothing bad happened, and that the marks lined up. To my surprise, they lined up, and the cam showed zero stretch - just as it should have! Woo-hoo! Half way there. Ok, now to see how far out the IP is. I just about fainted, then danced a jig, when I discovered the IP had NOT lost time with the crank & cam! YESSS! It was now at 11.5-12.0 degrees, as expected due to the new chain. I set it to 14.0 (actually a tiny hair advanced from 14, but close enough) and triple checked everything again.

OK, now to swap out the clip link for a rivet link. I found the OEM link that came with the chain was different from a Genuine Mercedes link (which I bought "just in case"). I'll go into details in my next post about the tools. I pressed the new (Genuine MB) link in, riveted it up, and looked around to see if I could spot the guardian angel that must have bailed me out. What should have been a simple job took waaaaay longer than expected, but at least it's done. Buttoned up the engine & cleaned up.

Results: Seems to be a smidge more power - not much, but perhaps a slight bit snappier off the line? Could be the infamous Placebo Effect. Too soon to tell on MPG. Interesting note is considerably more "diesel klatta" at cold idle. I mean you really notice it. My other 603 had a new chain and was always like that, but I didn't know that was the REASON! Hmmm. When cold, if you raise the RPM a bit, say to 1200rpm, the klatta vanishes (thanks to the IP timing advance device) and it's nearly silent. Back to idle, and KLATTA! The noise goes away when warm though (on both cars). Interesting phenomenon.

Anyway, sorry for the LONG post, but I thought I'd instill some real fear into you DIY's out there contemplating a timing chain job. It's not THAT bad but just be REALLY careful! I'd plan on 2 hours minimum, more like 3+ if you go slow & meticulous. YMMV, etc.


Best regards,
__________________
Dave M.
Boise, ID

1997 E420 - 154kmi (Bugeyes)
1994 E420 - 143kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 186kmi (Stinky Dirty)
Check out my website photos, documents, and movies!

Last edited by gsxr; 08-14-2003 at 07:57 PM.
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Old 08-14-2003, 07:53 PM
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...and here's that post on the chain crimp tools. Someone mentioned they use a chisel to remove the old link. I personally would not use anything that gives impact shocks to the cam & sprocket and don't recommend that. A Dremel would be much nicer. Using the ball peen hammer to "rivet" the new link is acceptable IF you use an anvil or sledge on the back side to absorb the shock, so no impacts are transferred to the cam & sprocket. These things have aluminum heads & cam towers with no separate bearings, definitely not something to beat on!!


===========
Hi again,

OK, here's the scoop on the timing chain tools. I've posted this link ad nauseam in the past, but for those just tuning in, here it is again. It applies to both diesel AND gas engines btw:

http://www.meimann.com/docs/mercedes/OM60x_Timing_Chain.pdf

The problem is that the document is rather obtuse, and contains one glaring error. It shows a part number for "diesel swage jaw" with one part shown, but "gas swage jaws" - note that's plural! - with two pieces shown. So do you get one or two pieces with the diesel jaws? Hmmm. Well I gambled & bought the part anyway, and was lucky - you do get both items. (whew!) Note to anyone buying the MB chain crimp tool(s). EACH piece is sold separately! You buy the "assembly tool", which is just a hunk of metal with a threaded shaft, then you buy the swage jaws (different for gas & diesel) separately! Ditto for the retainers, the clip-type "assembly" master links, and the "assembly" swage jaws. And the plastic case.

OK, so what's the deal with the assembly swage jaws? Reading the document made no sense until I actually got my hands on the the tools, AND the Genuine MB rivet-type master link. The OEM master link, in the Iwis chain box, has a "floating" center plate. It slips on & off easily. The Genuine MB link has a PRESSED on center plate! I guess the engineers really wanted a safety in place, if the outside link falls off somehow, the center pressed link would probably suffice to hold the chain together for tens of thousands of miles. The sucker goes on TIGHT. And THAT is what the "assembly" swage jaws are for (02-63-00). They neatly press the center plate on the link. Then you swap over to the separate rivet jaws, neatly press on the outside plate with the magnetized jaw, then flip it and rivet the pins. It was so neat you could barely tell the new master link apart from the rest of the chain links. VERY nice.

Anyway, I was very impressed with the quality of the OE tools (all made by Iwis, btw). They all worked perfectly. SirTools sells a chain crimper which is similar, but NOT identical, for a lot less $$$. The ST unit is about $175 on sale from IMPCO for gas OR diesel (you can buy the jaws for the other for an extra ~$50). I have not seen a ST crimper in person. However it uses the same "crimp" bit for both gas & diesel. And after seeing both side by side, I don't know if I like that idea. They are very different in size. Also, I suspect that the ST crimp bit does not press on the outer plate with a neat magnetized recess - you're expected to use pliers, I guess. Hmmmm.

The OE stuff is NOT cheap. The prices in that document are dealer COST and are several years old. Tack on an extra 10-15% for 2003 prices, then tack on another 20-40% for dealer profit depending on where you buy them. Check with Rusty and Randy, but also call your local dealer. R&R have to buy from a dealer themselves so there's less margin to go around, unfortunatley. My local dealer, who is normally a ripoff on all parts, actually wasn't bad on the tools! For the basic tool plus the diesel (or gas) swage jaws, figure ~$300 or so. Tack on another $25 for one of the two OM60x retainers, another $40 (!!!) if you want the clip-type links, and ~$125 for the press jaws to assemble the factory master link with the pressed center plate. Oh, and ~$35 for the nifty plastic case. Why yes it DOES get expensive in a hurry! You noticed, huh. I skipped all the chain breaker tools, opting to go the angle grinder route instead. Obviously not a cheap proposition, probably not worth buying IMO if you're only doing one chain. I got my original tool and gas swage jaws used, very cheap, in mint condition. I figured I'd just get the diesel jaws, and well that snowballed into something way more than anticipated (d'oh!!) I figure it was still cheaper than paying the dealer to do the job, and not much more than paying an indy shop.

And before y'all get too excited, I'm sorry, I don't rent or loan tools out. However I will happily help you do the job in my shop, provided you get car to Boise first!


Photos of the tool(s):

http://www.meimann.com/images/mercedes/W124_stuff/chain_tool1.jpg
(nifty plastic case)

http://www.meimann.com/images/mercedes/W124_stuff/chain_tool2.jpg
(inside the case - plus other non-chain MB tools in there too)

http://www.meimann.com/images/mercedes/W124_stuff/chain_tool3.jpg
(top is diesel, bottom is gas - and yes, I'll re-take this photo!)


Best regards,
__________________
Dave M.
Boise, ID

1997 E420 - 154kmi (Bugeyes)
1994 E420 - 143kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 186kmi (Stinky Dirty)
Check out my website photos, documents, and movies!
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  #3  
Old 08-15-2003, 10:25 AM
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Why not just use the clip type master link? I've put Hundreds of thousands of miles on them without any trouble.

P E H
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Old 08-15-2003, 12:00 PM
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Apparently there have been a number of failures of the clip type link in past years. Now, Mercedes specifically prohibits the use of the clip link for anything except to roll the new chain in. They only sell the rivet link with TWO pressed plates (not just one like in OEM/aftermarket chain kit). Given that a rebuilt OM603 engine is in the $8k range, I think it's wise to use the MB-specified link. Just my $0.02...
__________________
Dave M.
Boise, ID

1997 E420 - 154kmi (Bugeyes)
1994 E420 - 143kmi (Blondie)
1993 500E - 193kmi (Lollipop)
1992 400E - 186kmi (Stinky Dirty)
Check out my website photos, documents, and movies!
Reply With Quote
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