BTW: I just helped a friend tear into his 240D that broke a timing chain WHILE CRANKING.

The chain was wound AROUND the crank sprocket and back over itself. Broken valve cover and a bent valve or two.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

Ken, Ive never lost a cam chain ever although common sense suggests that on startup it would get maximum pressure applied I did once drive a car which had a very stretched cam chain on a petrol motor and at about 50 MPH it allowed the ignition timing to slip on the chain so the ignition timing was way out when things cooled down and I could have a look see.

I do not know why or how this happened but I can vouch that it certainly did happen but when the chain was replaced everything was once again where it was supposed to be which surprised me quite a bit as I thought I would be fiddling with the ignition timing to get things right. Of course the person who owned the car had cured his immediate problem by changing the position of the High Tension leads so the car would run. I think he had taken them back one point on the distributer to keep the motor running and then rotated the distributer so that the ignition timing was right. I've seen the same thing happen on injector pumps on truck motors as well the cam chain gets so stretched that it just skips over a few teeth on the injector pump so it gets changed before it can do any more damage.

Col

I have seen motors where the chain broke, had the pistons "eat" the valves, the "chomped" valves elongated the guides and broke the cam shaft, the camshaft punched a hole in the cover!

So then is it safe to say that every diesel is an interference engine due to the high compression?

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1984 190D 2.2 Auto 220k
2001 Jeep Cherokee Sport 70K
2004 Lexus RX-330 ??K
2005 Chrylser Crossfire LTD 6K

Play guitar? Go to www.cyberfret.com for free online lessons!

Actually it is far safer to say.

If you replace the Cam chain before it gets stretched too much you'll have a motor that runs for a very long time but if you neglect this one item then you are heading for a possible disaster. Once you loose a cam chain the only proper way to check what damage has been done is to dismantle the entire engine and then Magnaflux every component to check for stress damage, I would be looking particularly at the pistons, Cam Shaft/s and what they run in and then if the pistons are OK I'd forget about the crank and con rods but no doubt one of them would break and then wreck the motor anyway.

Of course a complete head job is one of the first things on the books and then we start looking for other damage.

Replacing Cam Chains on a regular basis is by far cheaper in the short term I've even seen Reco Motors with stretched Cam Chains that needed replacing before I would consider starting the new motor but then again that is more to do with the people rebuilding the motors rather than a basic design flaw, if they cut corners you get exactly what you pay for and have all the JOY of seeing another motor lunch itself right in front of you.

Col

The 61x engine don't suffer too badly when a chain goes, it usually just pops the cam towers and may bend a valve or two. Lower end will be fine, usually doesn't even mark the piston crowns.

Different story on the 60x engines, since the cam runs in the head, not in the towers the 61x engines use. This means it cannot pop the bearings in the towers, and if there is a hole in the valve cover, likely the cam shattered. This means a piston hit a valve hard enough to fracture the crank, so all the rods will likely be bent, pistons destroyed ($2500 a set, those!), and possibly a bent crank. Block may or may not be OK, depending on rod damage.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I would never try to run a chain until it breaks. It is a $120 part and fairly simple to change at that. Why try to get another 50k out of it? Does it matter if you change it at 200k vs 250k vs 300k? Wait longer to give the next owner or the junkyard another 50k on the chain you put in?

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1999 SL500
1969 280SE
2023 Ram 1500
2007 Tiara 3200

I originally started this thread in January when a 300SDL was advertised in the local paper with a broken chain for $2,000. I went out to take a look at it figuring that if the body was perfect I might make a lowball offer. It turned out that the car had 250k miles. It was sloppy in appearance and I deduced (using the cockroach theory) that there were many things wrong with it besides the motor and that the car was a real money pit.

The car came up in the paper in late February for $800 and a couple of weeks later I got a call from a friend of a friend who had just bought it. He had heard that I was a competent Mercedes diesel grease monkey (Isn't that what we all are?) and was looking for advice on how to deal with his new project.
I told him I had looked at the car and had passed on it because I did not think that I could bring it up to my standards without spending much more on it than it was worth. He said he had a nephew who works in a foriegn car shop who would help him get the car running. I recommended that he remove the head and drop the pan and do an autopsy on the motor before spending any time or money on the car.

I said "Is the cam broken?" and he said "What does a cam look like?"

I had several phone conversations with him over the next week and talked him through the removal of the cam which he said was not broken. Can the lifters collapse enough to under intense pressure and save the cam? He was able to fish the chain out of the case and said that it had broken at the master link.

I guess the chain was changed out and the mechanic did not peen the master link down so the master link backed out until it caught on something and KABOOM! Anyway, the plan I laid out for him was to remove the head and drop the pan and see if there were any bent valves, busted pistons bent rods etc.

I said "drain the oil and drop the pan" and he called back to tell me that the oil plug would not come out. Uh Oh!

I went out of town for a week and when I came back I noticed that the car is once again advertised in the paper (for $1650). I called him and he says he just doesn't have time to fool with it so he is selling it. My guess is that the nephew looked at it and gave him the same advice I originally gave him.

I don't think he will sell it any time soon. If I am in the area, I will go take a look at it because I am curious about how far he got. I'll keep you guys posted.

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL

Kind of interesting that a self-described "competant M/B grease monkey" will turn down such a vehicle for $800.00, for all of the right reasons.

However, a person who does not even know how to get an oil drain plug out of an oil pan will purchase such a vehicle, fully intending to "fix it up".

Oh, how fools are quickly separated from their money.

Brian,
I think that he and the nephew could have got the oil plug out.
The reason I wrote "Uh Oh!" Is that the stuck drain plug was just another cockroach (in the cockroach theory).
If the plug is stuck, how long do you think it has been since the last oil change?
A clue to this mystery... I doubt there is a "Topsider" riding around in the trunk!

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Tom Hughes
St. Louis
84 300SD
92 300D
86 300SDL

I doubt the PO knew what a topsider is, and the reason the plug is so stuck is they probably torqued it down trying to remove it, that is they may have turned it CW instead of CCW!
Or they may have taken the car to Jiffylube where they might even use an impact driver to install the darned plug
Actually this is a timely subject. I just had my local indy replace a timing chain for me. I haven't felt like messing with it what with the garage full and its been raining every week on and off for over 60 days here, and stuck in bed with gout!
The '83 300D has been my wife's car since about 1990 it had 216 K on it then and now it has 245K miles on it. The car was always a little sluggish esp cold, even with the ALDA tweaked.
The last time I had a valve lash I had the chain stretch checked and it was something like 4 or 5 degrees.
I had a chain that I had bought a few years back, when they were only around $50 (has anyone priced them lately? ) so I provided that and the shop supplied the tensioner and etc. Murphy must have been visiting the day they ordered the tensioner because it (a Swag) had a pinhole in the body and it was leaking oil to the extent that there was a fairly good sized puddle on my cement floor the day after I drove it home and changede the coolant (I also replaced the radiator that a body shop gave me free to replace the damage their employee did when the hood was up (I wonder if he leaned on it or what? Behrs don't like that kind of treatment, needless to say!)
So another few days passed before the tensioner was replaced under warranty but patience paid off, because I drove it last night and can say that now its really running well, like never before! The performance is noticeably improved.
The moral to this story is that I wish I had replaced the chain when I first got the car because I (err, make that my wife) could have enjoyed a better running car for all these years! And no worry about losing a chain and destroying an engine!

I believe the car is smoking less too, but I'll have to wait to pass judgement based on how dirty the chrome area on the bumper just above the tailpipe gets after about 3000 miles.

This has to be the cheapest and best thing you can do for keeping a hi miler diesel in top performance and reliability. Word to the wise: "Just do it"

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Someone who can't figure out a drain plug can do forensics on a chain master link?

How is the valve cover broken? What hit it?

Sixto
95 S420
87 300SDL

Either the chain came up and slapped it... or the cam broke and hit it... usually the latter....

If a car is desirable to me but has "unknown" damage I will buy it and take it home, if the price is cheap enough, figuring at the worst I will have to junk it and lose a small sum of money, while if I get lucky I will have a bargain. This works out well more than half the time, I must say about 2 or 3 times out of 10 it is a very easy fix, about half the time it is about what I expected, and only 2 or 3 times out of 10 do I have to eat a loss and then it's only a few bucks, because I didn't pay much over salvage price.

The other day I bought an 85 300SD with 126 body for $2000. It was cheap because it was being sold to settle an estate. I was not able to drive it, but heard it run. It turns out the (deceased) owner had the engine rebuilt and new tires put on a couple of months ago. Similar models around here sell for $4000 or $5000 privately, $6000 and up on a dealer's lot.

It needs exhaust, a taill light, and some brake work. It also has some rust spots. But I'm satisfied I got a bargain. I took a bit of a chance but even if it has some major problem, I can at least sell it for what I paid for it.

For a non runner with a sour engine, I might go $500 figuring to fix the engine. If it turned out not to be fixable I would look for a used engine cheap, or another car with a wrecked body and good engine, or just try to sell it for $500. The other possibility would be to part it out, and sell $1000 or $2000 of parts off it before sending the shell to the crusher.