Have you had a timing chain break!?
 

Let's have some input on chain breakages so as to get an idea of which engines are vulnerable.

I have seen several at the local shop but only have had one in the family. My Dad's 420S broke one on cold startup one morning a few years back resulting in bent valves and major rework.

Anyone else?

I appreciate the reply but I sorta wanted to get an actual head count of those, such as I, that have experienced a breakage personally. It seems a great deal of opinions keep popping up on this subject and I would like to get a consolidation of actual experiences.:)

Incidently, I doubt anyone changes their oil more often than we did on the 420S. It, still, jumped timing and broke with just over 100K on the odometer.

My local indy (MB trained!) say the following on timing chains:

Like a lot of other things, I usually check chain stretch every 30000 miles on customers cars. The only ones that seem to break without warning are the 380 single chains and the ones on 420s.

When the stretch gets as large as 8 degrees (cam at TDC, read pointer on crank), replace chain. More stretch and the 420 chain slaps on startup cold, and bam, it's rework time. Less than 8 degrees, doesn't matter if the guides are old, they don't break. He does replace the guides when he puts a new chain in, though, as the usually don't look to good.

He says he has never had any problems with this method -- he's been in the US since 1983 and has worked on MBs since he was a kid -- his dad had a taxi company.

Regular oil changes make a big difference -- those metal chains wear really fast if the oil is dirty or lacks lubricating qualities.

The best buy in the US is a 420 that has just had a broken chain replaced and all the related work done -- almost a new engine!

Peter

I of course, had a a timing chain break last Thursday night on my '89 190E 2.6. The engine had 218k mile on it but the top end was rebuilt at about 98k. Several thousand before I bought the car. The rebuild was done by a Rolls/Mercedes dealer in Atlanta. I don't remember if they replaced the chain, and I am not able to dig up the records at this moment. But I would be suprised if they did not put a new one in. Going over the cars records, they did not seem to miss an opportunity to take some of her hard earned cash. There was I think something like 2 or 3 full brake jobs, including rotors within 30,000 miles.

Anyway, the chain seems to have stretched at one of the pins and broke loose. It is not a clean break or fracture. I have not removed the lower cover yet and the chain will not come out. It seems to hang up on something at the bottom.

I have not been able to determine the extent of any valve damage at this time. The cam of course does not want to move very easily, and there is not much to turn it with. I may know more tomorrow.

Here again is a picture. This is the chain as I found it. It is not real clear, but perhaps you can make out the streched hole.

Is there ever any damage in the bottom? I kinda have this image of a chain zipping around at about a hundred miles an hour and when it brakes it wads up down around the crank sprocket. Ever any problems down there?

Don't know exactly, but I am going to find out. I tink most of the chain is intact. Just the other end that broke is caught on something.

Assuming that two cylinders will have valves in the closed position. I just checked numbers 1 and 4 by using my compression gauge setup. I pulled out the check valve and screwed the adapter into the spark plug threads. Then I fired up the compresser to 60 or so lbs and attached the end of the hose to the disconnect. Then I heard the rush of air passing though the exhaust as is went past the bent valve. At least 1 and 4 are bent and I assume they all are. I don't think I heard anything pass through the intakes, but I still have the air filter and cover attached.

How am I ever going to convince my wife that these are reliable cars?

I had the chain break on the 300SE as I was cruising on the freeway at 110 km/p.

It just happened, and the engine died while the car was gently coached to the emergency lane. Smoke blowing out for a while, and only the air-cond worked ... though not very comfortably.

Got it towed to the usual MB garage and had it fixed on warranty since the chain was just changed 2 months prior.

It required a head job - valves, and a new chain. I saw the chains in shambles ... bits and pieces of what was once a beautiful link.

Southern Son,

Thanks for posting this thread. I apologize for not responding as an experienced chain breaker as you requested. I also hope you recieve some replies from those with first hand experience. This is a very interesting subject for me as well.

Michael,

I continue to study your photograph. It's interesting the way the pin seemed to pull loose. When the engine failed did it seem to lock up all of a sudden in any way? The reason I ask is, by looking at the chain it almost makes you think that something happened to lock up the camshaft causing the chain to be "yanked loose". Only a thought, you're the one that's living through this. We are all just interested in learning from this, and want to help if we can.

Everyone,

Michael said the chain had been recently changed, notice the color of the chains side plates. Is this possibly an inferior aftermarket chain? I just got a new aftermarket chain for my M103 and it's sideplates are the same color. I'm a little concerned. Any comments?

Good luck,

Last year my mechanic was working on a 420sel with a jumped timing chain. He re-did the valves, guides etc and after putting the engine together and firing it up, he heard a ticking sound. He was trying to determine the nature of the ticking - when Bang - there was a loud noise and the engine was freewheeling. Upon disassembly, the new chain was broken in two places 4" apart similar to the pix above. AFTER ONLY 3 MINUTES OF RUNNING!! It was an after market chain. He rebuilt the engine again with a mercedes chain and the car is still running great. Don't know if it is co-incidence or if these after market chains are poorly constucted. My mechanic thought something had jammed in the engine but could not find a possible cause. Because the new chain has been working for over a year now - he was pretty sure it was the after market chain that was just defective. As an aside - when the after market chain broke #7 piston got damaged (don't remember how) and scored the cylinder wall resulting in the block being sent out to get a new sleeve installed.

I hope to have tha harmonic balancer off tonight, then I can rotate the cam by placing the chain on both sprockets and turning the crankshaft. I'm hoping the cam will turn. If not, then we know why the chain broke. It does look to me as if the chain was pulled apart.

The strange thing in the above photo is that the chain is not broken on the side where it gets pulled from the crank but from the other one (if of course I imagine the picture correctly) which undergoes much less force!

The car was going about 75 mph when the chain broke. When I heard the chain break, I could swear I thought that there was a momentary slight acceleration. Maybe this was because the crank no longer had to pull the cam. After the slight hickup, the engine lost power and I coasted a long ways.

Right now I'm going to put the front end up on stands so I can get at and jam the flywheel so I can get the balancer off.

I was most concern when after changing the timing chain 2 months earlier, it broke on me while cruising.

I was adamant that there might have been a manufacturer's defect as the chain was torn to bits. All that was left, and retrieved, were tiny metal schrapnels of not more than 1.5 cm each (roughly of half an inch). Nothing was left of that chain.

Since then, I just hope that chains don't break so easily.

Can anyone tell me how many links I should have on my chain? Again, it is for a 190E 2.6, the M103 engine I believe. I have retrieved the chain, and I think I may have it all.

I don't know if I should try to turn the cam while it is still on the engine, or just go ahead and take the head off first.

You will probably hit a piston if you turn the cam. I don't think I would try at this point, maybe just continue disassembly and repair.:)

Hey guys:

Never use an aftermarket chain with a master link and clip rather than the MB type endless chain where you have to grind the ends off a set of pins to free a link, and must crip the pins on the new chain's removlable link. The clip will always fail, usually at speed.

Brian:

Get the stretch checked on your 420 at least every 30,000 miles. Quick and easy method on my previous post (set cam to TDC mark an look at balancer to see how "late" the crank is). Less than 8 degrees is OK, more means replace the chain.

Chains usually last nearly forever except in 420s, some 380s, and the 190 (early). My 220D has something in excess of 150,000 on it and no problems with the chain.....everything else is shot, but the chain is fine!

Peter

psfred, I am curious.....how does the M/B dealership roll in a new chain if it is 'endless'?

There is nothing wrong with a replacement chain that is of quality build. (read 'made in Germany')

For those contemplating this job, the official service manual from M/B on the V-8 engine, M116.96 (3.8) and M117.96 (5.0), states on page 05.7-320/1 F3, "A repair chain with connecting link is available for repairs. If only and endless timing chain is available, the chain can be opened prior to installation by grinding off both pins of a link and subsequent installation by means of a connecting link."

As I said, just get a good quality chain and you should be just fine. No need to get endless and fool with crimping.

You MUST crimp any replacement chain! Don't use a clip master link type chain. The clip master link is only good for temporary use while rolling in the new chain. DON'T USE THE CLIP MASTERLINK FOR THE CHAIN TO BE RUN!!!!!!!

I believe that just because a chain is "made in Germany" does not mean that it is necessarily a high quality chain. It's certainly a good indication. I am curious if there are any first hand experiences with breakage of ANY aftermarket, single row chain.

Have a great day,

While on this subject, how many hours of labor should it be to replace a timing chain, tensioner, and upper rails (specifically on a 190E 2.3 8v)?

Rags

The chain that broke has a mark on each link. The mark is:

JWIS

Is this an after market chain?

Looking at the broken link, doe the hole for the pin seem unusaully large?

Larry, who told you not to use a clip master link for repair? Also, which brand names made in Germany would you be leary of? (just curious, Larry)

Michael:

The links are made up of pins and plates with a spacer between the plates. The pins are held in place by being "riveted" -- that is to say the ends of the pins are expanded by swaging them with a swaging tool that drives a cone-shaped device into the end of the pin. Since the end is now larger than the hole in the plate, it stays put.

A master link type chain has one link with larger pins that have a slot cut in one end. A spring clip goes in the slot to hold the pins in place.

When you buy a new chain, it will have one plate with the pins swaged in on one side only. The other plate is free.

One then grinds or files the swaged end off of a pair of pins and uses the fancy Mercedes tool to push the pins and the attached plate off. This breaks the chain. One end of the new chain is attached to the old chain with the new pin set without the plate, and the engine is rotated by hand until the new chain is pulled all the way though and both ends are on top of the cam. Both parts of the chain, the part goin in and the part going out, must be kept in tension, and preferably in contact with the cam sproket to avoid jumping a tooth.

When the new chain is in, the pin set is put through the ends and the fancy Mercedes tool anvil is reversed to crimp (actually swage) the pins into place after the plate is installed.

Pretty neat, since you end up with an endless chain without a weak link.

The picture almost certainly shows a "master link" type chain, as the pins on the master link must be larger in diameter to have the same diameter as the other link where the slot in the pin is cut for the snap clip. This is why they break -- there isn't enough material around the larger hole. The snap clip can also break or get snapped off if the chain slaps, and with an oil pressure tesioner, the chain slaps every time you start the engine.

It also doesn't look anything at all as heavy as a typical MB chain.

Peter

timing chains and links
 

There is no reason NOT to use a 'master link' on a replacement chain. The pins and holes are EXACTLY THE SAME as an 'endless' chain, and they ARE NOT a weak link. The clips do not vibrate off if properly installed. In nearly 50 years of working with and around equipment of all kinds with many roller chains, I have NEVER heard of or experienced a master link failure.

The chain that failed in this picture it would be most informative in the adjacent side plate was removed and the roller pin examined for wear. That is what failed on the broken link the roller pin pulled out of the inner side plate.

That kind of failure indicates the chain was severely overstressed (jammed by broken guide?) this assumed the hardness of the failed side plate was correct , which can be verified by hardness testing.

Fred, who told you the pins of the master link are larger in diameter? Why do you think the chain slaps everytime I start my little 380? (it doesn't)

Which 420 engine are we talking about here in regards to chain failure? Is it the 119? (Isn't there more than one?, I might be wrong.) Has anyone had a 119 timing chain fail? At what mileage?

mplefleur,

I just got my replacement chain and I counted links. Once assembled it will includ 95 pins. The way I counted was two pins at a time and came up with 47 and an extra left ove meaning a completed chain would contain 95 pins. I hope this helps and keep us informed.

Everyone,

It's unbelievable that something like a timing chain turns into something controversial.

o I did not state that there was any aftermarket German made chain that was no good. On the contrary, I was ASKING if anyone knew of any aftermarket chain that was recommended or NOT recommended.

o To answer the attack about the clipped master link, this came from the Haynes manual and I have so far followed it with success. If you want to take issue, call the Haynes publishing company.

o I too, in my earlier years, raced motorcycles and never lost a clipped master link. However, there is availability of crimping tools and crimped master links are what is typically supplied. I have also heard pro techs here on mshop say to use the clipped type for rolling in a chain, not for regular service. Additionally a new MB does not come with a clipped master link installed. This all seemed to indicate that there is a valid reason, although I don't know what it is. I was merely trying to pass this information along.

You are free to put YOURS together with baling wire if you wish and I promise I won't say anything about it hence forth.

Have a great day,

Larry, I am sorry that you felt attacked? I merely asked your source of information. Wow! Or was it the difference of opinion that made you feel attacked? Dang! Woahhh, dude!

As for the haynes manual giving better information than the Merdedes Shop manual, I think I'll go with the advice and service procedure in the M/B manual. It states a master lind can be used. As far as the question about your suspect of German brands, you were the one that said because a chain comes from Germany does not necessarily make it a quality chain. Is it not logical that I would ask which brands from Germany you find suspect?

I appreciate the good information from all that replied to my original post. I do wish we had all discovered more on broken chains from those that have actually experienced it.:)

make it an endless chain
 

I would strongly urge making the timing chain an endless chain by using the correct tool to deform the pins on the master link - and not use a clip-type master link.

In another life, I am an American Honda factory trained Honda motorcycle technician (only honor graduate ever = 93 or better on all tests for the 8 classes taking 8 weeks to complete), shop foreman, technical advisor to American for the S. Texas region; after leaving became the supervisor of maintenence for the largest tree care company in the US (responsible for branch offices in Texas) and maintained everything from chainsaws to medium heavy-duty trucks - to name some of my experience in the area of mechnical/technical care of engines/vehicles.

Honda tech bulletins required changing timing chains for their overhead camshaft engines to endless chains from clip-type master link chains. This resulted in far fewer timing chain failures caused by the master link. Recall that many of these engines have redlines in the 8,000-10,000 and higher RPM range and that racing engines have tremendous forces exerted on them caused by redlines above 10,000 RPM.


Drive chains were endless and clip-type master links were not recommended - especially for the larger displacement engines (some may recall the early 750 inline 4 cylinder Honda motorcycles had many failures - many were caused by clip-type master links and sunsequently the change to endless chains).

Clip-type master links for timing chains can be used, but I would not. If you use a clip-type master link than ensure that the clip is completely in the grooves on the end of the pins and that the open end of the clip is facing away from the direction of rotation (if the open end is facing in the direction of rotation, then centrifugal forces will force the clip open and result in catastrohic failure). On racing motorcyles (especially road racing) the safety rules required endless drive chains (or safety wired master links which had smalll holes drilled in the master link clip and then high strength safety wire was threaded through and then secured by tightly twisting the ends together usually using a special tool to twist the wire - the safety wire we used came from the aircraft industry). On dirt bikes we used to safety wire the clip-type master link to the outer plate (obviously we were using very fine high strength stainless steel safety wire that did not interfere with the chain to sprocket teeth contact) and prefered to use endless chains or drilled pin safety wired master links.

I have the MB manual (1991 Ed.) for the 615, 616, and 617.912 engines (covering the 220D 1968-1973, 240D 1974-1977, and 300D 1975-1981). This manual shows a clip-type master link of the e-type clip, one clip used on each pin of the master link. The e-type clip is called that because it looks like a very rounded letter "E" when held up and orientated like you would write the letter "E." My previous discussion has been about the larger clip-type master link that engages grooves in both pins at the same timeand provides a much larger contact area on the side plate and, hence, is much stronger than the e-type clips. The e-type clips have a much smaller contact area on the master link side plate and, hence, provide far less strength. Also, the etype clip does rotate, the open end will eventually face the direction of engine rotation, and centrifugal foces can cause the clip to fail. My MB manual shows the e-type clip and these clips look like they have the much smaller contact area on the side plate that I am writing about (page no. 05.4-320/3) and this type of clip will rotate. I cannot agree with the MB manual in the use of clip-type master links, especially the e-type clip. Also, MB requires/recommends using an endless chain when doing an overhaul - should you use anything less when just replacing the timing chain? I think not.

If you have the e-type master link, then I STRONGLY urge you to NOT use them. I strongly urge you to not use the larger master link clip either.

To provide the maximum protection against timing chain failure, I recommend using an endless chain. The bit of extra effort to make an endless chain to avoid costly failure and spending 1,000's of $ to repair your engine.

You can rent a timing chain crimping tool from Performance Products for about $35 plus S&H for a two week rental. PP also sells timing chains that like many of their other parts have a 24 month transferable warranty - an unheard of warranty and shows the confidence PP has in the parts it sells. I have one of their timing chains on my 300D made into an endless chain using their tools and it works like the original. PP provides installation instructions for the timing chain and info on how to use the chain crimping tool. If you decide to make your chain an endless one using the PP tool, then I can provide other info to help you use the tool.

Hope this helps.

Tom

tcane, that resume is very impressive. I wonder how the education of the german engineers that wrote the service manual that states the use of a master link is permissable would stack up to your education?

Southern Son,

Does the MB manual mean a CRIMPED master link or a CLIP master link? A crimped master link still qualifies and may be referred to as a master link. They may mean using a master link is okay so that the chain can be fed in. They may not mean it is okay to use a clipped master link. If they do, I would be interested to know.

I apologize for claiming that I was attacked. Things have been very tense for me for a while and the REAL attack in New York has not helped my attitude any. If I was overbearing in my original post in which I warned against a clipped master link, I was only trying to help. I apologize if my tone was incorrect while giving that recommendation. The consequences of a failed chain in one of these engines involves several thousand dollars damage plus a good bit of frustration. BTW I WILL continue to use CRIMPED master links in my engines, and everyone is totally free to use what they wish in their engines. It's a free country.


PS I read the end of Mr. Cane's post about the E clips. I hope no one expects that the long C type clip will substitute for this.


Have a great day,

ISP Problems and Clarification
 

I have had a lot of problem with my ISP and was not able to add info and edit my first post. Please re-read my post as I hope to have clarified and completed it.

All I can say about the MB engine manual that I own is that I have found info in it that does not directly apply to my 300D (see my post about injector nozzles and whether to use the nozzle plates/sealing washers). I do know that most Honda service manuals available when I was associated with Honda did not contain all the info that was available to the dealership - much less the info American Honda had. I am fairly certain that MB service departments have 1,000's of pages and/or CD-ROMS with much more info than what the public can buy. I am not inferring that the MB manual is misleading and/or wrong - I am saying that we may not have all the info available. I have also found info about MB vehicles in service manuals at my library that is not in my MB service manuals, especially the Mitchell service manuals. However, these other manuals do not have info contained in the MB manual.

The method that anyone uses to attach their timing chain is up to them. I am only providing my opinion on the method I know will work - endless chains are far stronger than chains using a master link (the e-type or c-type clip). However, I do know that some/many will take exception to my suggestion/knowledge/opinion since my background is on less-well engineered vehicles than the engineering used in MB vehicles and my actual experience on MB vehicles is limited to my personal 300D and some with one medium-duty MB truck (GVW 40,000 lbs.) - so be it.

Good Luck!

Tom

Last comment and suggestions
 

One observation about timing chains using master link vs. making it an endless chain. Did your original timing chain have a master link? If not, then that fact speaks volumes about making a replacement chain endless and not use a master link.

However, if someone is going to use a master link then in addition to making sure the open end of the clip is facing in the opposite direction of engine rotation the sharp edge of the clip MUST face outwards. These clips (both the e-type and c-type) are stamped out when made and there is a round edge (this is the side that was struck by the cutter) and a sharp edge. The sharp edge will provide a larger more sure contact area on the grooves cut into the pin. The sharp edge of the clip can be easily found by fealing it with your finger.

Last, do not twist, deform, or in any manner damage the clip so that it will have its original shape and best chance of staying on the pin grooves.

I am curious about whether or not anyone's MB engine manual goes into the details of using a master link similar to my suggestions? My MB engine manual does not contain any of this info.

Good Luck!

Tom

The reason the manufacturer uses the endless chain in the original installation is simple; the engine cover is off and during assembly it is easy to put on the cheaper endless chain. The manufacture of a master link costs more since it must be machined for the clips. It has nothing to do with strength.:)

Larry, I would like to know if there are, in your experience, some name brands made in Germany from which one would be wise to steer clear or is this just an idle statement?

I've a couple of questions about my chain that broke.

Each link is stamped I believed with "JWIS". The chain has 96 pins.

Is this a MB chain?

It was not the "Master" link that snapped. The link that was used to connect this chain together is chamfered or beaten along the whole edge of each rivet while all other rivets on the chain is beveled only on two opposite sides.

Note by the attachment that the pin that pulled out of the link does not have the roller or spacer. Where could it have gone, or was it never there? I can't believe that it came off. No other pin has a roller that has any kind of indication that it is biginning to separate.

Had to buy the "triple square" socket to get at the head bolts. Will have it off tomorrow. I am waiting for my parts. My brother who has a German auto shop in Arizona is sending them out, but who knows when a plane can have them here?

I went to the machine shop that has my Harley heads to find out when they will be done and look into them doing the work on this head when to my suprise they were closed and apparently in bankrupcy. Mayfair has been doing great work for 30-40 years. I hope I am wrong. How do I go about finding out about getting my heads back?

Southern Son,

I apologize for not putting a question mark on the end of my original question. I will say again for the third time, I am asking a question here. I don't know which brand is a good brand and which one is a bad brand, that is why I am seeking the experience of others with aftermarket chains to see if there is one to stay away from, or one that is known to be high quality. Call my statement an idle statement if you want. I was merely seeking the benefit of the experience(s) of others.

Additionally, it is not the STRENGTH of a clipped master link that is in question. It is the possibility of the clip coming off. If you wish to debate whether or not the clip can come off or not, that would be what you should debate, not the STRENGTH of the closing link. Many people continue to use the term master link interchangably for a clipped master link as well as a peened master link. In the case of a factory chain, every link is the same, they are all peened together. The only difference in a peened master link and a clipped master link is the means of holding the plate in place. When replacing a chain, using the crimping tool properly, you will probably not be able to recognize the closing (master) link.

Have a great day,

Michael,

I am sorry to hear about your machine shop closing down. I hope you can find out how to get your Harley heads back. I have put lots of hours into cylinder heads before in the form of port work and other tedious time spent, it would have been a loss greater than the value of the heads had I run into what you are experiencing.

I thank you again for continuing to supply information and photographs of your failed chain. I very much expect that the pin and roller are in the bottom of the pan. It wouldn't be too much trouble to remove the lower oil pan, or maybe you've already done that.

Best of luck with the project,

I was thinking that my chain was intact and that the end of the chain that you see in pic with the exposed pin was the pin that was pulled out. I wonder if there ever was a roller on that pin. I will look in the pan but I can't see how the roller could have come off.

I haven't removed the pan. You have to lift the engine to do this don't you? That is not something I wanted to do. However, if I do remove the pan, how much more trouble if it to do some bottom end work? I expect that is where most of my oil pressure is dissapearing.

Michael,

Yes, I forgot, this engine has a one piece pan. I expect that it wouldn't be too bad to raise the engine enough to remove it.

I expect that there was a roller in place at one time. The way the chain is made, the rollers are in place before you put in the connecting link.

Good luck,

Do yo think I can do enough to the bottom without too much trouble? It's one of those "While I am at it..." things.


I was wondering if the chain was missing that roller when it was installed. That would extra stress on the link, especially when about to enter or exit the sprocket. Over time this could wear out the holes the pin goes through to the oint is cannot hold the tension and pulls through the remaining metal.

Just thinking out loud (per se).

Michael,

Do you mean in the form of replacing bearings and such? There was a very good article in the Star magazine about six months or so ago about the fact that the bottom of these engines far outlast the top. When my cylinder head demanded attention at 170K miles, I found the bottom to be in excellent shape. These engines typically respond extremely well to cylinder head work. Mine has gone about 30K miles now since I did the top and it has great oil pressure and no oil consumption problems at all.

I expect that missing roller is in the pan, but there is just no way to be sure without some disassembly. Most likely it would stay in the bottom of the pan and not cause any problems, but there are no guarantees of this. If you had a magnet small enough to fit through the drain plug hole and move around in the sump, you very possibly could get lucky and fish it out. The drain plug hole is large enough that it would be worth investigating.

Best of luck,

Yes, I meant bearings and such. The bottom end has 220k on it and I have absolutely no oil pressure reading at idle while hot. Increasing rpm by about 200 can increase it to about 1000. It has not been confirmed via a true pressure gauge though. I can only attribute this to bearings and journals. If I do decide to, what can be replaced without too much trouble?

Michael,

Wow, if the oil pressure is really totally gone, you would expect some serious clearance problem somewhere. Since you're working on the top end anyway, examine cam bearing surfaces and journals to see if there is obvious wear at that area, if so that might be where your oil pressure is going.

I think we both know, however, that the most likely area would be the main bearings and journals. You won't know until you mic the crank journals and the mains can't be measured properly without at least partially removing the crankshaft. If the engine is this bad, do you have facilities to just pull the motor and do it all? With the exhaust loose, which it has to be for the head to come off anyway, the rest of the work involved with pulling the engine would not be much more than raising the motor. You will just need to be careful with connections and mark them well.

With the engine out, you can then more easily remove the crankshaft for grinding if necessary. I'm sure you know that when you start down this road, one thing often leads to another.

Another thing that may help you decide is the bore condition which you will, of course, know after the head is off. If you find the bores have a heavy ridge, then your crankshaft is more likely to need attention, and the engine would best come out at that time anyway.

It's really difficult sometimes to know where to draw the line. It almost always turns out to take more time and money than your original plan.

Good luck,

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.

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.

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?:confused:

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, 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