I would like to ask this forum members about your timing chains and rail guides. How many cars you see with high mileage without any timing chains and/or guides replaced? Whats the milage and if anybody replaced their guides and at what milage and how they looked? And onother probably stupid question in my opinion: will car run good with guides broken besides of course possible engine damage?
Thank you

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod

I have a 1989 300E with 188000 miles now and it still has its original guides, tensioner and chain....

I plan to have the all the parts replaced at 200,000 miles. Since that is the mileage that people say is a good time to replace, assuming you do not hear any very odd noises coming from the front of the engine.

Anyways, if I had a Mercedes V-8, I would change the parts at 100,000 since the chain is much longer and makes sharp turns in its path to wrap around everything......

If you are afraid of it breaking like I am, drive as gently as you can until you save up enough money and/or find a good shop and/or time to get it done.
I don't have the confidence to replace that part since if I mess it up, my dad would be very angry with me and my car would be permanently disabled. And I am NOT going back to riding a bus to school!!!!! I am too spoiled for that again!

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2006 BMW M5 "Heidi" @ 109,000 miles
2005 MBZ C55 AMG "Lorelai" @ 165,000 miles
1991 MBZ 300E "Benzachino II" @ 165,000 miles
1990 MBZ 500SL "Shoshanna" @ 118,000 miles

(On the hunt for a good used M103 engine as of 6/10/23, PM me if you have one to sell!)

My 420sel had almost 150,000 miles on it before the timing chain, rails, and tensioner were changed - but that is with oil changes every 3.000 miles. I sure would not let it go that long in a Mercedes V-8.

Timing chain longevity depends on the make and model of the car.

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Auto Zentral Ltd.

Just replaced the guides, tensioner & chain on my son's 86 420SEL. The car has about 106k Miles. The guides were broken and the chain very stretched.

I replaced the upper rails at 107K miles. All parts looked good. I will be doing the chain this summer. It appeares to be streached by the fact that the cam timing assembly markes are out of align by about 1/8" and there is about a 10 second start up period where you can hear the chain, until it gets tight. I need to get the timing tools before I atempt this.

John Roncallo

How true (from what I have read).

The good news Victor, is your M103 in question, is one of the best for longevity... I don't think it has a replacement interval so if your oil has been, and does get changed regular just listen for chainslap when you start it up, and change it if you ever have to get in there deep to do somthing else... maybe if you did the front timing cover seal after 250,000 or so... You might want to check it for strech if you want to be on the safe side.

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-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html

Okay, you all have me a bit concerned. I have about 270K on my 1990 350SDL and it is all original (timing chain, guides, etc). Runs great, good acceleration and gets about 27MPG. Should I be rushing to my nearest service center to have these parts changed before catastrophic failure? One of my previous MB diesels, a 1979 300SD went 365K miles without anything being replaced. A few years back I had inquired at the local MB dealership and they said there was no replacement schedule for this.

Thanks,
Brian

Timing chains last a very long time on I6's. Actually they should be gear driven but MB cheaped out!

They don't break often, but they do stretch. It really depends on how the often the oil is changed and what kind of engine it is.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

First of all, my 88 300E has 279,000 miles with original chain and components. This particular engine probably has a system that is as robust and reliable chain system of any MB engine.

Secondly, Hatterasguy, with all respect, having a gear system, rather than a chain system on an overhead cam engine of any kind is a totally impractical approach for anything short of an all out, no holds barred, double throw down race engine. It would take a number of gears to link the distance between the crankshaft gear and the cam gear(s.) On an OHV engine, it can be done with as little as two gears because of the cam being very close to the crankshaft. When the shafts are far apart it takes a number of idler gears to make up the distance. That means that with all those gears, the slack will add up and make for a very sloppy system with poor cam timing after not too many miles of wear. There is no way to take up the slack in gears as they wear as you do with a tensioner on a chain.

In a race engine, these gears would be replaced often, in a street car you would not want to do that.

Additionally gears are typically noisy, a characteristic that MB goes to a lot of trouble and expense to engineer out of their cars.

Have a great day,

Rolls Royce used gears for years because Royce hated the idea of timing belts/chains. It took one guy 80 hours to polish and make the gears for an engine. I wonder how long they used them or if they still do.

I am 90% sure the I6 in my dads F150 is gear driven.

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2016 Corvette Stingray 2LT
1969 280SE
2023 Ram 1500
2007 Tiara 3200

Yes indeed the Ford I6 and several other American I6's over the years use gears. That's why I pointed out in my post that OHV engines are good candidates for gears because the camshaft center is very near the crankshaft center. That means that one gear on each shaft is all that is necessary.

The way that Detroit has dealt with the noise problem with gear driven cams has been to use nonmetallic gears. This does not make for a super durable setup.

When the shafts are farther apart as in an OHC engine, it will require the use of several idler gears between the driving and driven gears. Again, this results in a build up of the slack in the gears. In the case of a OHC in a V configuration it will take probably 8 gears at the very least and that would be for a SINGLE OHC.

I also fully expect that the Rolls Royce engines you speak of were OHV or flathead engines. There again the shafts are close enough to require only one gear on each shaft.

Have a great day,