I just returned from the MB dealership here in San Antone. I picked-up some bolts special ordered from Germany to rebuild the mechanical governor that controls the amount of advance of the injection pump on my 300D (believe it or not, MB only replaces mechanical governors and not rebuild them, cost $504 to $580 to replace versus about $30 to rebuild, I used grade 8.8 bolts bought locally to temporarily assemble the mechanical governor and get my car on the road until the special bolts came in).

The asst. parts manager confirmed that his technicians/mechanics use master links that are crimped with a special tool and that they do not use clip type master links. To aid our discussion the asst. parts mngr. got a timing chain for my 300D and we inspected the master link - it is the crimp type to make an endless chain. I asked him why the MB engine manual I have shows the clip type master link - he did not know why, only that the crimp type master link is stronger than the clip type.

Also, the MB timing chain for the 300D is made by JWIS and these initials/service mark are stamped on the timing chain's side plates. The replacement chain for my 300D purchased from Performance Products is also made by JWIS and comes with a master link that has to be crimped with a special tool that I discussed in an earlier reply. The PP timing chain has a 24 month transferable warranty - the MB replacement chain a 12 month warranty. I have used JWIS chain in the past and they were all equal to the OE chain or better.

Neither the MB timing chain nor the PP timing chain come with a clip type master link - only the crimp type master link requiring a special tool to perform the crimp operation. PP rents the tool for $35 for a two week period plus S&H.

Larry your observation that the clip type master link is used for replacing the old chain by attaching the old chain to the new chain is probably correct (since the MB manual does not say). Like you, I cannot see MB using a clip type master link for continuous service and the clip type link is only used for assisting with the replacement of the old chain to ensure the chains do not become separated and turning a straight forward job into a much more time-consuming repair. I can see the clip type master link being a MB special tool to assist with replacing an old chain.

Michael, your pictures of the timing chain indicate a major failure probably in the oil reaching the chain. The oil lubrication path diagram for my 300D shows that this timing chain is lubricated from outflow from the first bearing journal (the closest bearing journal to the front of the engine) and when I replaced my front crankshaft seal I did not see an oil pipe or oil passage that would directly oil the timing chain. Meaning the timing chain on my engine is lubricated indirectly - which is a method that I have seen on numerous engines Your engine probably uses the same or similar way to lubricate the timing chain - indirect. Your comments about low oil pressure indicates a major failure of some kind (oil pump, failed main journal bearing, cam bearing, some crack or break or blockage in one of the oil passageways, failed oil filter with pieces clogging an oil line/passage, etc., etc.) and will have to be found when you disassemble the engine - as Larry wrote about. I would suggest being very observant as you disassemble your engine and look for the cause of the failure. Finding the real cause of the failure is very important because the cause must be found and corrected before rebuilding your engine - simply replacing broken parts with new ones and then running your engine may/probably lead to the same failure again.

Finding the cause may require more extensive disassembly of your engine than you may want to do or have planned for, but I think you and Larry will agree the cause must be found to avoid a repeat failure costing lots of $. As I recall, you wrote that this engine had been overhauled not too long ago (correct me if I am wrong) leading me to believe that the cause leading to the first overhaul was not found and fixed, or was not fixed completely/correctly.

Your picture of the timing chain shows a chain made with split rollers that fit onto the pin and the picture shows one pin missing a roller. Split rollers do come apart far more easily than non-split rollers. The lack of a split roller coupled with the torn side plate show a probable loss of oil pressure leading to a failure (perhaps stopping the crankshaft or cam from turning) causing damage to the timing chain- as you and Larry have written about. I am sure the chain had the roller when it was replaced (provided it was replaced) and the failure caused damage to the roller and that is why it is missing. One would hope that the people who did the overhaul did not re-use a timing chain that was missing a roller.

An inspection of the pan and the debris (if any) in it will tell a lot. As Larry said, you should remove the pan to see what's in it.

When you rebuild the engine I know you will lubricate the various moving parts that are usually done (pistons/rings/pins, cylinder walls, rods, bearings, cam, valve guides, etc., etc.) - I suggest that the new timing chain be lubricated with engine oil. Simply rotate the engine and pour some oil on the top of the chain, rotate it a bit more and pour more oil on it until the entire chain has been oiled. I have not read any recommendation to oil the timing chain like this before initial start-up, but I believe pre-oiling the chain will extend its life since it is indirectly lubricated. This is how I lubricated my 300D's timing chain before start-up as well as other timing chains on the numerous engines that I have rebuilt - none ever failed.

Michael, I will read with interest as you write about your engine and the cause of the failure.

Good luck!

Tom

I have a couple of comments to add.

I don't believe that the clip-type master link reduces the strength of the chain. The strength is determined by the pin and side plate strentgh. This is a question of reliability and I firmly agree that the crimp-type master link is more reliable than a clip-type.

There is another mode of failure for the e-type clips that wasn't discussed. The clips can actually spin on the pins due to vibration and wear the pin away. I have never used e-clips on a timing chain, but I have had this failure mode with other applications of e-clips.

Finally, there is a type of chain known as a "true roller" where the rollers are machined bearing surfaces, not the split rollers like shown in the picture. True rollers are quieter and roll on the chain wheels, which reduces friction and wear. I am familiar with them from small block Chevys, but is there a choice for a "true roller" versus split roller for MBZ? If so, the choice is obvious. I didn't even think to check which type of chain it was when I replaced the one in the 300E.

Your missing roller could be smashed on either the crank or cam gear. It's worth a look.

__________________
D.H.

04 ML500
02 E430

Experience is something you don't get until just after you need it.

mplafleur, before tearing down the bottom end you may want to ask a mechanic familiar with the 190 to confirm the existence of a bypass valve in the oil pump/filter. If there is one and the spring or seat is messed up, you can experience low pressure. Hopefully this will be the case.

Mr. Cane,

Thank you very much for your research and insightful, informative post. I now feel much better about the JWIS chain that I received to use on my 300E.

Southern Son,

Thank you for starting this thread that has turned out to be so insightful and valuable.

I apologize here in front of God and everybody for any unclear post that I may have offered. I will do my best to respond henceforth with only information of a technical nature and not ask any questions of you that may be construed as some sort of accusation.

Have a great day,

I have been rather occupied lately with world happenings and my German partner trapped in Canada.

I would add a couple comments based upon a quick reading of the last four pages. Maybe the most important would be to try and put some perspective to this discussion. One post way back worried about explaining these problems to his wife.

I have never had a car that experienced a broken timing chain. I have been involved with fixing hundreds. I will never have a car that experiences a broken timing chain. I have never seen a timing chain break that didn't fit into one of two distinct conditions. The first condition is the fragile POS chain rails in the V8 heads (all 116/117 versions except the early models with aluminum rails). The second is chain systems running loose. Almost all diesels with broken chains were rattling for months due to tentioner failure or wear or vacuum pumps that were doing similar.

These problems all happen to vehicles long after I will ever own one (Its unlikely I will ever own a car with over a 100k on it - my 84 928 which I have owned since 1987 has 91k on it), so I won't ever have that experience. I say this for perspective. Simple maintenance can keep these very maintenance free systems from significant risk.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

From what I can tell in my Mercedes engine service manual, there is an oil pressure relief valve. I will have to remove the sump, use special tool 001 589 60 21 00, whatever that is.

It appears the broken chain is a Mercedes part. No more will be known about the cause until I finish getting the head off, and look in the pan.

Over the years, I've purchased 4 manuals for this car: electrical, HVAC, chassis, and engine. The engine manual has almost nothing on the crank and pistons. Is there yet another manual I am supposed to buy?

Group 3 in this manual only has:

03-310 Checking, renewing and tightening conrad bolts.
03-324 Renewing front crankshaft radial seal.
03-327 Renewing rear crankshaft radial seal.
03-324 Removing, installing belt pully, flywheel damper and hub.
03-410 Removing, installing flywheel or driven plate.
03-420 Machining flywheel.

Kind of inadequate for the job I have of rebuilding the bottom end.

__________________
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)

Michael, I have found the bottom ends to be built like a tank. Therefore, you may consider leaving the crank and pistons alone and proceeding with replacing the oil pump. If it turns out to be the bottom end after all is put back together, then you will probably be better off to just get a rebuilt long block or salvage from junk yard. Tough call but as I said I doubt the bottom end is suspect.

Note: upon replacing the oil pump in my 380 I had the misfortune of stripping the middle bolt female threads in the housing. This happened before I had even torqued to 7 #'s. I used the old housing to guide the drill bit for the heli-coil, sprayed my zinc chromate onto the heli-coil, cinched it up into the tapped hole, torqued the bolt (into which I had drilled a couple of holes in the heads for safety wire) and saftied the head to an extension on the housing. This was really simple and not worth all the worry I experienced.

Michael:

Hard to believe the MB engine manual does not contain detailed info about the crankshaft and related components/assemblies.

A call to MercedesParts may yield info about their service manual or CD-ROM that will cover in more detail the info you need. If they can't help then call Performance Products and inquire about the info their CD-ROM manual has for your engine (800-243-1220, you may want to order their parts catalog covering your MB because their web site does not list all the parts they stock). Also, Haynes may make a manual containing the info - the one I have for my 300D is very good and goes well with my MB manuals. I recall buying my Haynes manual at Auto Zone, a phone call or two should determine which parts co. has the Haynes manual.

Tom

__________________
America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.

A friend of mine broke the chain in a 190E from 84.
This car was not properly serviced.
I kept telling him to fill oil because he this car was famous for
large oil consumtion.
One day he told me to listen to some strange sounds coming from
the car when he reved.
I told him that the camshaft was making noise and it had to be serviced my a mechanic ,he ignored it reulted in a brake down within a week.
He the bought a Mazda 323F <- but this car sounds awful all the time.
Excuse me all Mazda fans out there.


Pelle

I agree that the bottom of the M103 engine is well built. However, that has little to do with what could be WRONG with the engine. I understand that Michael is not the original owner of the car. If the oil was not changed very often, or if it was allowed to get low, any engine can cause premature wear under these conditions.

The last thing that should be done is to start replacing parts without investigation. The only way to properly investigate is to start doing exploratory surgery as Michael is now doing.

Good luck and please keep us informed as your investigation continues.

Larry, if it were not well engineered and terribly built, would that lead to possibilities of what is WRONG with the engine?

your funny........

Okay, I'll try a different choice of words. What I mean by what is WRONG with the engine is which parts need machining or replacing in the engine. How's that?

Again I AGREE!!!!!!!!!!!! These are well built engines. However, there has never been ANY engine that does not have some sort of failure, something wears out or suffers from some sort of problem such as what happens if it runs low of oil. How well it is built has nothing to do with these type of failures.

Now how does this make me funny? I am merely pointing out what anyone who has ever torn an engine apart will understand. You take it apart, measure, examine, investigate and correct. Now what about THIS is funny?

I will get a head start on offering my apologies to Southern Son, since I know he will SOMEHOW be offended by these statements. I've apologized to him after my comments before, so maybe some apology ahead of time will work better.

So what did I say to offend you this time?

Have a great day,

Bless your heart, Larry, I am sure it will get better.

Now now guys. I appreciate everybodies help, especially Larry for his many posts and guidance, Southern_Son for starting the thread, BlackMercedes and psfred for adding their input.

The head is off and all the exhaust valves have hit their respective piston. All pistons have slight dents in them and otherwise look fine. No intake valve shows indication of hitting anything. This engine is apparently has an interference head, but not by much.

The cam rotates fine. Seizing was not the cause of the chain break. The cam looks fine (to the untrained eye). The contacting surface of the head to the cam (I don't know what to call it. There is no journal or bearing) looks ok. There are small dark specks in the dull metal. I don't know what to make of them.

__________________
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)

Michael, I am surprised that all pistons were hit unless, of course, the chain jumped a few teeth and after a few hits, let go. I suppose the question for ones experienced in this would be 'how much stress can the top of the piston take before needing replacing?'. Do you have any wear ridge evident at the top of the cylinder from the rings? I would bet the block and cylinder wear are still within limits.

I wish you luck in your parts salvage.