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  #1  
Old 09-28-2002, 09:14 PM
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Join Date: Sep 2002
Location: new jersey
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timing chain

i believe i read somewhere the 1984 380sl was without the the dreaded timing chain problem

am i correct? did the problem stop in 1983

thanks
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  #2  
Old 09-28-2002, 09:16 PM
TANK
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Please be more specific. What problem? If you mean replacing at 100-150k. That's a given, or at least have an inspection of timing chain stretch. Alternative is to not have it checked and possibly destroy your engine with a snapped timing chain.
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  #3  
Old 09-28-2002, 09:24 PM
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timing chain

i was refering to the double or single

i read all 84 380sl came with double t chain

Q 2 - i have almost 100k on my 84 380sl - u mentioned a chain adjustment

haven t had that done / is this something i should do / is this a routine check up on this car /

thanks for the info
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  #4  
Old 09-28-2002, 10:02 PM
TANK
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Yes, between 100-150k, you should have the stretch checked to be sure the timing chain is not too far out of spec. If it is way out, they should replace it. If it's not way out, at least you know you are ok. I remember your question of single vs double row coming up before but I do not know the answer as I have a diesel, and I knoq all diesels of my year had double row. I replaced mine at 134k and because it is 16 years old. I figured, $450 of insurance was worth it rather than having it break and replacing a $4500 engine.
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  #5  
Old 09-28-2002, 11:01 PM
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Tank,

To quote you: "I replaced mine at 134k and because it was 16 years old".

Now there's a case "if it ain't broke, don't fix it".

Mine is 22 years old and 236,000 miles and I wouldn't think of replacing it until it has reached 3 degree elongation. Besides, the chains don't break unless something else breaks like the vacuum pump or chain guides and broken parts get into the running chain. When the chain elongates, it just causes the cam timing to be off slightly and even less for the IP. Only if the chain gets elongated so much that the tensioner will not take up the slack, will the chain jump a tooth or 2 and cause the valves to hit the pistons.

And when I do (if ever) replace my chain, I'll do it myself for about $75.

P E H

Last edited by P.E.Haiges; 09-29-2002 at 09:27 PM.
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  #6  
Old 09-28-2002, 11:10 PM
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Litletrees,

One way to be sure if you have single or double timing chain is to pull off a valve cover and look. If your engine originally had a single chain, and you are not the original owner, the chain could have been replaced with a double chain without your knowledge.


That single timing chain was a real screw up by the wonderful MB engineers. How could they be so stupid?

P E H
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  #7  
Old 09-28-2002, 11:46 PM
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people

i will have the tension checked very soon

read somewhere if u look at the chain u can tell if single of double

circle for single chain

oval for double

thanks again for info Tank and P E H
jim
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  #8  
Old 09-29-2002, 02:20 AM
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Litletrees,

I don't know what you mean by circle or oval but its easy to visually determine single or double chain.

Single chain is about 1/2 inch wide and double chain is about 1 inch wide.

Single chain has 2 rows of connecting links and one roller between them. Double chain has 3 rows of connecting links and 2 rollers bewteen the links.

P E H
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  #9  
Old 09-29-2002, 07:59 AM
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oval or circle

P E H

thank you

the oval / double ---------------- circle / single

visual difference between single or double chain

i read in a post easy visual id of chain ----------- ?

as i am new to the mercedes car - i am gathering info in case of

u have given me clear info

the person i bought the car from didn t keep records
had the car for 12 yrs - changed w/pump - trans pan gasket - and wiper liquid container - regular oil changes
he said the person he bought the car from was a friend

in 12yrs he put less than 50k on the car

i am 3rd owner - car now has 99k

when able i will post pics of the car
again thanks for sharing
jim
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  #10  
Old 09-29-2002, 03:11 PM
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According to Frank Barrett's Illustrated Buyer's Guide to Mercedes Benz, 1981-1983 380 engines had the single row timing chain. Beginning in 1984 MB began using the double row timing chain.

With the single row chain, (which by the way was unique to the U.S. - in Europe they always had a double row timing chain) if the oil wasn't changed frequently, friction under load would cause the chain to wear and stretch. If a single row chain jumped a tooth on its sprockets, the valves would hit the pistons, with expensive consequences.

Still, even with the doulbe row timing chain, the chains do stretch on these M116 and M117 engines over time, because the chains are long and change direction many times as they travel from the crank at the bottom up to each cam on each side of the "V".

Most members and techs on this site recommend replacing the chains approximately every 100,000 - 120,000 miles. 4 degrees of stretch is considered the time to change the chain.

Further, it's not just the chain that's the problem. The chain guide rails are made of plastic, and become hard and brittle over time, as well. As the chain stretches it becomes loose, and starts to rattle and bang and slap against the guides. It usually happens at start-up, but when the chain gets loose enough and the guide rails are old and brittle enough, the chain will slap against the plastic and it'll break apart. Plastic pieces will get stuck in the chain and the sprocket, and bam!, you've bend a camshaft, pistons will hit valves, etc.

I've found from reading posts on this site, that's it's more often a loose chain breaking old guide rails, than a loose chain jumping a sprocket that causes an engine failure.

Either way, your car is due for a timing chain replacement and upper guide rails. You asked about a chain adjustment, but there is none.

Just like Nike says, Do it. Do it now.
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2001 E430, Bourdeaux Red, Oyster interior.
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1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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  #11  
Old 09-29-2002, 06:41 PM
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timing chain

suginami

thats the stuff i need

thanks for your time and info

will look into having the car serviced this wk

jim
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  #12  
Old 09-29-2002, 09:23 PM
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Litletrees,

I still have no idea of the circle/single oval/double thing you mentioned.

Imagine a bicycle chain layed flat so the pins connecting the links are horiziontal and you are looking straight down. This is a single chain.

Now imagine two bicycle chains layed tightly side by side with both inside connecting pin ends touching each other and horizontal and you are again looking straight down. This is a double chain.

You can see that the double row timing chain, like two bicycle chains, is about twice as wide as the single timing chain. And the double row timing chain has about twice the strength of the single chain.

Chain stretch was mentioned by others. This is not technically accurate. The pins and the rollers wear, oval on the inside of the rollers and flat spot on the pins, so the chain becomes elongated but not stretched like a rubber band.

Another thing, the only time the chain becomes loose is when it elongates beyond the capacity of the chain tensioner to keep the chain tight. A competent MB mechanic can inspect the timing chain and tell you if it needs replacement. He should also inspect the chain tensioner for proper operation.

P E H
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  #13  
Old 09-29-2002, 10:24 PM
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Regardless of how the chain stretches, it still does, and the tensioner is apparently unable to keep the chain tight.

It's something I've never been able to figure out. Why couldn't Mercedes engineer this properly so that the tensioner could effectively keep the chain tight? Also, why did they use plastic rail guides that break as they get old? These two issues are so systemic with these engines, they'd have to have their heads in the sand to not know about it.

It is such common knowledge among technicians about replacing these chains every 100,000-120,000 miles, like it's a part of the engine's normal maintenance.

Strange, huh?
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2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".
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  #14  
Old 09-30-2002, 03:34 AM
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Suginami,

The chain tensioner can only keep the chain tight up to certain point. Even if the chain tensioner was able to keep an elongated chain tight, The cam timing would be off with a severly elongated timing chain, thus the chain will have to be replaced to have the cams timed correctly.

The chain elongation on the V8s is greater because of the many more pins and rollers and the wear of each. Since the second driven cam in a V8 is so much farther away from the drive sprocket (measuring along the chain travel) than in an inline engine, the timing chain must be replaced more often in a V8.

The plastic chain guides are better than the old rubber coated aluminum chain guides. Possibly it was difficult to do accelerated life tests on the plastic guides. Maybe a better material has not been developed yet.

But just think how much better the double roller chain is than the the rice burners with a belt that has to be changed every 60,000 miles. Although the belt costs less than a chain, the total cost is more because of the labor to replace the belts many times.

P E H
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  #15  
Old 09-30-2002, 07:49 AM
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Join Date: Jun 2001
Location: Northern Calif. (Fairfield Area)
Posts: 2,225
Suginami pretty well summed it up. Considering the mileage and your comment about regular oil changes, I don't think I'd do the chain yet. I would suggest replacing the two rails on the left bank. The inner rail breaks off and rides the cam gear up which causes valve timing to jump and bends the valves on the left bank only. Hoses and V belts almost never break anymore being of technological advances in materials. Perhaps they are making better rails now.

Peter
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