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, 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.

Wow, it looks like my idea to apologize ahead of time works! That's great!

Michael,

I expect that the pistons are not hurt by the valve contact. That is not to say that they are not in need of replacement due to wear. Micing the cylinders will tell that story. If you can't catch a ridge with your fingernail, I expect cylinders, pistons and rings are probably okay.

Have you been able to examine ALL of the timing chain associated components such as the guide rails and such? You will be able to get the head back in shape relatively easily. It obviously will take 6 exhaust valves and you should have them replace the valve guides at the same time. Be careful not to drop any of the tiny "cups" that fit between the rockers and valve stems.

Good luck with your further exploratory surgery.

Have a great day,

Thanks guys. I was going to check for a ridge line this morning before I left for work, but was rushed by my daughter to get her to basketball practice and forgot. I assume you mean a ridge after any deposits are removed.

I too was suprised to see that ALL the exhaust valves were hit.

While removing the rocker bolts, I found the threads still wound around the bottom of one of the bolts. I think it was the exhaust side of number 3 or 4. I guess a helicoil is the answer here.

Is the dull wear normal on the contact surfaces on the head? There are dark specks in the surface material, but no pits or scratches.

Michael,

Glad to hear about your priorities, sounds like they're right on target. Your daughter comes first.

First off, when removing or installing the cam and it's stands and rockers, remove or tighten the bolts evenly so as to not break the camshaft.

You should be able to remove enough of the deposits with nothing more than your fingernail. If your fingernail does not remove enough so that you don't catch a METAL ridge with your fingernail, then you have a ridge. Removing the "deposits" with a ridge reamer will also remove metal, making the ridge left meaningless for determining wear.

I still don't totally understand your questions/remarks regarding the specks on the head surface. But, given the type of failure you are analyzing, this very well may be a clue.

Good luck,

Michael, do not use, and do not let anyone else use, an abrasive wheel to clean the gasket material off the head and block surfaces. The grit is difficult to remove and will chew up the cylinders. You need to take your time to scrape the residue off. To protect the inside of your cylinders (should you decide to leave the bottom end alone), I found it useful to get a drafting compass to draw and cut out circles of manila folders to put over the top of the bores. You can tape the paper to the outside of the cylinders by using a corresponding circle of masking tape just a little larger. Then get a nylon bore brush (gun cleaning), do not use a metal brush and do not chase the threads with a tap, the nylon will clean the threads just fine. Blow out the bolt holes with air. When putting the head bolts in, be sure to liberally apply oil to the bolts. These are just some tips you may find helpful. Let me know if you should have anymore questions.:)

SS - why do you recommend NOT tapping the threads out?

Engatwork, the last time I tried to clean up the threads in aluminum using a tap it ate up all kinds of aluminum filings. I found no trouble in cleaning up the head bolt holes on my 380 as described above. I did not have to use inserts. The bolts torqued up really nicely. However, it was necessary to tap the hole for the insert for my oil pump bolt that had stripped out of the hole. Anyone else with experience on this subject?

I looked closer at the cylinder walls. There is absolutely no ridge whatsoever. In fact, all the cross-hatching is clearly visible. I'm thinking so far that there is nothing I need to do to the pistons and cylinders.:cool:

The head parts will take a few days to get here. I have to find a shop in the area that can work on it.

I'll start taking the rest of the engine out. At minimum, I will get a new oil pump. I will take a closer look at the crank, bearings and journals.

Thanks much for the info on preparing and renewing the head and block surfaces.

Southern Son offers good advice. That is not the first time I've heard of the woes of those air operated gasket surface cleaning products. I have a simple scraper that uses a single edge razor blade. It's a little time consuming but does a very good job without introducing grit into the engine.

I'm not surprised about your cylinder walls. That's a good sign. My biggest worry now continues to be your oil pressure. This brings up further thoughts. When you fished out the timing chain pieces were they very dry? With low or near zero oil pressure, this could be related to the chain failure. As others have advised, analyze everything until you find the source of your oil pressure loss. It's common for everyone to replace the oil pump when pressure is low, but it sounds like you already know that the problem is most likely elsewhere.

Thanks for the minute by minute reports and good luck,

The cam and head were well oiled and the timing chain had oil on it. It had been allowed to dip dry for a few days and with much wiping with a shop towel, it is still a bit oily to handle. Since the timing chain does not travel through the pan, where does it get its oil from?

The timing chain gets its oil from the front main bearing, plus on some MB engines, any oil from the oil pressure relief valve is deposited on the chain, I don't think it got much from there in your case. With low oil pressure, if the front main has excessive clearance, you would expect that the timing chain got plenty of oil.

With the cylinders in good shape it just doesn't sound like an engine that was abused in any way. But, if it was ever allowed to run low of oil the majority of such damage would be to bearing surfaces.

Keep on inspectin'.

Good luck,

Head parts on the way. Found a shop today. Will get the head to the shop tomorrow for disassembly and cleanup.

Drained the oil pan tonight. I only found some pieces of the chain rail, but I have yet to remove the pan. I've removed almost everything on the topside, except for the A/C. I'm trying to remove that without losing my charge. I have a 20lb can of R-12, but I don't want to use any if I don't have to.

BTW:

The engine has never been low on oil that I know of.

It has been VERY hot however, when I had some cooling problems a year or so ago. I've had to replace the radiator 4 years ago. Water pump 3 years ago, the heater core, circulation pump, and some vacuum operated valve last year. Everything on this car leaked. Now I've a vacuum leak inside. :( (I get hot air ALL the time)

I'm considering picking up a high milage late model M-class next year. What's the record on that one?

Michael,

I wonder if your oil pressure sender is okay. You keep giving us more information that indicates that the bottom of the engine is in good shape, the cylinders looked good, the engine has been kept in good repair with frequent oil changes and has never run low of oil. All this is just making me wonder about the sender. There was a poster a few weeks ago that was getting totally scared to death over low oil pressure only to find that replacing the sender did the trick.

It's too bad you could not have put a mechanical guage on the motor while it was still running to check this. Then you would know whether or not you should dig deeper at this point.

I think that your discovery of the guide rail pieces in the pan is the first real clue we've seen about what led to the failure of the chain. Given what the chain looked like, it just HAD to be broken by something locking up and yanking the chain apart. A broken guide rail would sure do that.

At this point in your investigation, it is beginning to look as if replacing the timing chain and ALL associated components along with the fresh head might be the thing to do. It's really hard to imagine the bottom end being bad. But if you could prop up the engine enough to slip off the oil pan it would let you pull down a few bearings and take a look. It wouldn't hurt to slip a mic over a few journals while you're there.

BTW, I totally understand your desire to not lose any of the gaseous gold R12. You should be able to swing the a/c compressor out of the way and hang it somewhere with coat hanger wire to keep from straining the hoses. I have only a little R12 left in my 35 pound can myself, and I'm taking every step I can to preserve it.

Hang in there and good luck,

I have taken out my oil pressure sending unit. It there a way I can test it?

The only way I would know would be to use an ohmmeter on a known good one and compare the two. If you knew someone with the same model, it would be worth putting it in their car temporarily to see if it is the culprit. If it is indeed bad, I believe it would be a good indication that rebuilding the timing chain system and top end of your motor will get everything back in good shape.

Is there anyone in Michaels area with the same model 190?

Good luck and God bless America,

Things are progressing, albiet slowly. It turns out that all valves, but two intake valves were bent. Here is the worst exhaust valve.

Head is in the shop. It's all clean now and pressure tested fine. Amazing that all the guides are ok. So are all the pistons I hope. I will inspect them closer this weekend when I take the lower end out. I can then look for wear on the rod and main bearings.

I got a box of parts today. Chain, guides, head rebuild kit, head bolts, but no valves and only one set of seals. :( I will have to call about that tomorrow. I was hoping to give the shop all the parts on Monday.

Well, the family is here with a movie and popcorn and I just got home from work. Popcorn for dinner is fine with me.

God Bless America!

Sorry, here is the picture:

Michael, the good news is..once you have it all back together, it should remain in good shape if you monitor the condition of the chain. As I suspected under another thread heading on your engine, it appears to me that the chain did get loose, jumped a few teeth and experienced interference resulting in chain separation.

That engine should be good for another couple of hundred thousand miles upon completion (maybe a great deal more!).:)

Well, I just got the block out. I took the pan off. I found a couple more small guide rail pieces, but I also found half a chain roller and a small part that came from I don't know where.:confused: I'll take a picture and post it on a new thread and see if anybody can identify it.

I also took off one rod bearing and one main bearing. I'll describe those tomorrow after I get some sleep.

Well, the engine block is sitting upside down inside my garage, the head is at the machine shop and I've got a bunch of parts on my table.

The valves and seals go to the shop tomorrow.

Otherwise, I have:

Timing chain
Tensioner
Timing chain rail
Timing chain guide
Oil pump chain
Oil pump chain guide
Head gasket kit
Head bolts
Crank gear
Front crank seal
Rear crank seal
Oil pump
Oil pressure sender
Motor mounts
Main bearings
Rod bearings

Am I missing anything? Is there a need for the tensioner? It is just the insides (spring and pressure pin).

Michael:

I assume you have had the crank checked for journal diameter and condition -- if not, please have it done if you don't do it yourself! New bearings won't fix damaged crank journals.

If you took the pistons out, you will need new rings, too. If they looked OK, and you didn't remove them, you are probably OK, but if they have been removed, it is foolish at best to put old rings back in.

Check the piston pin bushings for wear -- there should be no play in them if you twist the rod -- any play means the bushing is bad and needs to be replaced.

If it were me, I'd have checked the bores for wear and re-sleeved them if necessary, and checked the rods to make sure they aren't bent -- not very common on these engines, but since it is apart already......

Peter

The bores shows no wear and have the original crosshatching. I don't want to touch those so I am being very careful not to move them around. I don't want the rings to move as I don't expect them to seat a second time.

The rod bearings look worn. The mains look ok but for some long scoring. The crank looks fine too. I will check for wrist pin/bushing wear (very carefully) when I take the crank out.

If I find problems with the piston pins, then I will have to rethink what I want to do. I've been told different things as to whether I can just put on new rings without reboring or honing and having it reseat properly. This means another trip to the machine shop. This was to be an inexpensive rebuild.

Michael:

Have the crank checked for taper and roundness as well as size of the journals, rod and mains. If there is anything out of tolerance, you will need to have it ground, polished, and balanced (which requires the pistons, alas).

Just don't spin the pistons in the bores -- up and down won't hurt anything as long as the rings stay in their usual range -- don't push them into or past the ridge at the top. They go up and down a lot when the engine is running.....!

If the the crank journals look nice and clean, with no scratches or wear marks, you are probably OK -- my brothers (and the one in the short block he bought) was OK, but the bearings weren't right, so were shot. Minor imperfections can be polished out without grinding, so long as the diameter isn't greatly changed (as in still within stated tolerance). If you don't know how to use a micrometer, have the measuring done by someone with a metric mic set, no SAE with "translation" -- it isn't accurate enough.

Scratches imply dirt, and that in turn implies crank damage. Sorry.

All you need to do if the pistons have to come out is put new rings in after cleaning the pistons. Check ring clearance (side to side), although if the crosshatching is fine, I cannot imagine the pistons are worn. The the wear is less the 0.002" (a ridge you can distintly feel, no more) at the top of the cylinder, you don't need to do anything except maybe "deglaze" with a ball hone (have a shop do this, specify no diameter change!)

You will still have oil pressure problems with new bearings if the crank is bad, so you will have to decide what to do. If it was run out of oil, there is enough babbit on MB bearings to save the crank at the cost of ruining the bearings, so you are probably still OK, and will have proper pressure.

If you don't want to re-do the crank, get some plastigage and check the bearing clearance with it -- the smaller the better above 0.0005" -- you may have some trouble getting the proper size, as most auto supply places hire help who think Chevy 0.005" is about right!

Good luck!

Peter

Oh, I forgot to say, it won't be cheaper to have to do it twice from saving money the first time!

I'm facing the same dilema with my 300DT -- do I just put a head on it and ignore the low compression, or do I re-do the entire motor? Head is $1200 plus gasket, etc, motor is $3500 more, (pistons are $2500 from my usualy supplier) plus 12 hrs R%R and 50 hrs rebuild by the time book -- and since I've not done one of these before, many more hours, I'm sure. The damned thing had better run forever after I rebuild it!

Peter

Peter,

Thanks for the tips. I certainly will be extremely careful in making sure I don't rotate the pistons. I don't want those rings to unseat. Since they look fine with absolutely no ridge, I don't want to do anything with them.

I'll plastigage the crank when I get the new parts in and let you know what I find. I'm only going to hold onto this car for no more than another year.

When I rebuilt the head on my '75 300D, I think I paid $100 each for the pistons and those were Mercedes parts. This was in the late 80's. My brother gave them to me at cost, but I don't think the mark-up is THAT much. The turbo parts must be extra special.;)

chain roller gone
 

the picture you provide shows a missing roller. In all probability the missing roller (in peices) is in the oil pan. It (and it's next door neighbor?) probably cracked and fell off. It may have jamed in the sprocket when it came loose and that is what pulled the chain in two.

What caused it to crack? It got hit sometime after manufacture (dropped, hit on ?) or it was slapping around , or the sprockets are worn.

However, I noticed the adjacent roller to way too short!! There should not be a lot a end play on the rollers!

I did find the rest of the roller in the pan. I first found a full length section that was about 1/3 the circumference. Then two days ago I found the rest. The remaining 2/3 was split in two, not down the length, but across the roller, at about 60/40 in length.

Michael:

The pistons for the turbos have a wonderful oil channel precision cast to route the oil spray around the crowm and back down the sides for cooling. They also have the steel ring for the top compression ring, and holes from the oil cooling channel into the oil control ring. About $425 each, I think, as opposed to $110 for my brother's 75 330D. Fortunately, if the ring lands aren't worn, they can be reused with new rings as long as the cylinder walls weren't too bad -- I've seen them with an extruded lip where the ring was banging up and down on the land due to execessive piston to sylinder clearance.

If the 87 wasn't such a blast to drive, bad engine and all, I'd never have bought it, but in good shape will be very nice transportation for a long time -- I tend to keep my cars forever.

MB puts a ton of babbit on their bearings, unlike GM (0.010", plated), so unless you got something in there that ate up the mains, you will be all right. MB cranks are HARD! My brother broke his, but that was because the PO had it rebuilt, nasty job, used oragne silicon sealant on everything, and a chunk seems to have shot down off the oil filter housing (in front on the old 617) and cut off the oil suppply to the thrust bearing (#2 main) -- starved the #2 crankpin, so it failed, too, classic sharp radius crank failure, cracked from the inside edge of the journal to the outside of the crank. It had been broken for some time -- one side was black from oil dirt -- before it blew. Block seems to be OK, but we got a short block just in case, and used that. Pistons, except #2, in the old block were fine, didn't discover that until we had bought new ones. The #2 main was spinning in the block, bearing was welded to the crank, and the motor ran!

Peter

I used some plastigage on the rod and mains with the original parts. The clearances on the mains are .004 and the rods are .003. Good for a Chevy.

I don't know what they are for the replacement bearings. I am hesitant to use the stretch bolts again.

The mains are not stretch. So I put a new bearing in and the clearance went to .003. Only down .001. Is that enough? Keep in mind that I did not replace the bearing on the opposite side.

Michael,

Sounds like you're still moving right along with your engine.

I have a Haynes manual that was written in England, so terminology is sometimes a problem.

It says "Radial play of crankshaft in bearings" is .030mm to .050mm. I believe that this is main bearing clearance tolerance.

It also says "Radial play of big end bearings on crankshaft" is .030mm to .060mm. I believe this is rod bearing clearance.

Since .1mm = .004inches, these "radial plays" are quite tight compared to the Chevy's I've built. .05mm(the max main bearing clearance) would be .002 inch.

I hate to say it, but it appears that this may be where your oil pressure was going. Good news is that you should be able to find a good crankshaft shop that could grind the crank and get everything tight again. Since it sounds like you now have the engine out, maybe this wouldn't be too much more trouble.

These are just some thoughts for you. I'm sure you'll want to consult an official MB manual for clearance spec's before taking such a step.

After rereading your successive posts, maybe by replacing the upper half of the main bearing, you will get your clearance where it needs to be on the mains. Remember, using plastigage will not allow you to check for a flat crank. But maybe you're close enough with new bearings. Keep checking and good luck.

Best of luck,

Michael:

Bearing oil clearance for the 617 (the latest I have handy) is 0.002" to 0.003". At 0.004" I'd expect oil pressure loss. If you come down 0.001" by putting in a new half, you may be OK, but you won't know until you put in both halfs.

Also, make sure the bearing shell is CLEAN, and the cap and recess are, also, or you can end up with NO clearance (bad, bad, bad!). I don't use shop cloths when putting an engine together, only the high quality blue towels -- they shed much less lint. Make sure the shells, caps, and recesses are oil free when using the plastigage, too!

You can check for flat spots on the crankpins with platigage, but you have to turn the crank 90 degrees between each check, a huge pain. Get a micrometer and have someone show you how to use it -- you will be good enough in a couple measurements to see if the cranpins are tapered or out of round, anyway.

Having the crank ground will require new, undersized bearing shells and balancing, in which case new rings as the pistons have to come out (they have to be on the crank to balance it.....)

As you don't plan to keep the car, if the crank is nice and shiny, with no obvious wear spots where the babbit on the bearing rides and no scratches, and you can get 0.003" or less clearance on all journals, you can get away with just new bearings. Any visible damage to the crank, and the new bearings will look like the old ones very quickly. Your call!

Peter

Peter,

Thanks. Again, I don't want to take the pistons out.

The crank is shiny, no scratches, and no wear spots. I don't plan on keeping the car for more than another year. Replacing 1/2 did get it to within spec.

I'll take the whole thing out and put both halves in and see what I get.

I just bought an engine stand and got the thing off the floor. Now it almost gives the impression that I know what I'm doing. But it's all you guys that get the credit!

Just for background: I'm an electrical engineer working for Visteon. I test powertrain control modules that we sell to Ford, Jaguar, Astin Martin, etc. so I know a bit about the control side of the engine. I grew up on a farm where my dad did all our own wrenching. He was a mechanical engineer for Chrysler (Mercedes now). I don't like to pay anyone to do something that I can do. I'm 40 and going back to college for my masters in Electronics and Computer Control Systems (whatever that means). I just learned to fly last year and I'm a year or so away from my black belt in Koei-kan.

If I can help anyone out with anything, I'm more than glad to do so.

Michael:

You are really a true he-man if you are wrestling that block around on the floor! An engine stand is the ONLY way to go! Unless MB really lightened them up, they weigh almost as much as an american V8 bigblock!

If the crank is unmarked, and that includes no visible tracks from the bearings, put new ones in and go. Not the purist approach, but if you aren't going to drive it forever, let the next owner worry about it (My brother says you need to have the rods reconditioned to, buy he never takes a motor apart without a complete rebuild!). The worst that will happen is that the oil pressure will drop again. MB nitrides the crank 0.030" deep, so it is hard to hurt them.

Check the clearances again with the new bearings, and if you are near 0.002" go for it.

Peter

Michael,

I'm glad you are getting help here, but you're the one working through everything. You get the credit for keeping another MB on the road.

I'm a doubleE myself and have done all sorts of control systems over the years for various different systems varying from oil production to automatic conveyor control. Doing engine management control would be a real kick for me.

Keep up the good work,

PsFred has some very good insight into the cleanliness of the job using towels. I am not much help with the specific engine you are working on but another thought for the shop towels would be the use of paper towels. Paper fibers will degrade and get purged from the engine upon the oil change.

How long do you have to wait for the black belt upon recommendation in that discipline of martial arts? I am not that famililiar with that one.

Pete,

The use of a comealong, and a heavy chain have been very helpful to me. If I didn't, the block would still be in the car! I'm not big: 5'10" and 165 lbs and of slight build.

I rebuilt a '75 300D about a dozen years ago. I know I had the block re-bored because I remember my brother shipped me 5 new pistons at about $100 each. Back then I didn't think anything could be that expensive. I remember that I had to give them to the machine shop as each was stamped with its' size. I recall transporting the block in the back of my Escort, but I don't remember having any help getting it out of the trunk. I was doing the work at my moms farm and I'm sure no one was there to help me. I do remember it was d*** heavy!

Southern_son,

I don't like shop towels, they have very poor absorbtion properties. I usually use good cloth towels (my wife hates that!) and paper towels. I like that suggestion.

Koei-kan is an Okinowan based karate. I've been learning for about 5 years now. The belt promotions at our dojo goes from white, yellow, blue, 1st green, 2nd green, 3rd green, 1st brown. 2nd brown, 3rd brown, then black. I'm currently at 2nd brown and should be testing for 3rd brown this winter. Tests usually come every 4-6 months for those green and under. At the brown belt level, I would be suprised to have a test in less than a years time since the previous. The work on the car has me going to class only once a week at present.

Larry,

I actually spent about 4 years writing engine control software for the Formula One race car that Ford sponsered in the mid-late 80's. That was for the Benneton team. I then moved to work on the Service Bay Diagnostics tool used by the Ford dealers. For the past 4 years I've been working on the system used to test engine control modules. I was contract for 14 years at Ford. I finally hired in and got 1 Ford paycheck before we got spun off into Visteon April of last year.

Michael:

I finally got down to the shop (and ordered more parts....): there is no part like the screw you found in the oil pan in the 190 engine. Hans thinks (like I do) that it is a temporary link to draw the chain through that is supposed to be replaced with a crimp link. Probably why the chain broke.

Yeah, one guy can move that 617 block, but what a pain! Weighs a ton (we figure the 617 is about the same weight, all decked out and ready to go in, as a Chrylser Hemi). All that cast iron....!

My dad was an electical engineer, did automated control systems for assembly machines -- alternator winders for Chyrlser, oil cooler machines for Chrylser, horn testers for Ford (that one was in the basement, spent days punching holes in electical panel boxes), etc. Pretty spiff stuff for the late 60's. I heard a rumor he worked on the control system for the Patriot missle, too, which would explain why he took FORTRAN classes about 1972. Cool stuff.

I can't do math worth crap, so I'm a plant physiologist working as a chemist.....

Peter

Well, I got word today that my head is done. But I'm not done with the block yet. I have to get it cleaned up and do those crank and rod bearings. I am also replacing both front and rear seals. I would like to wait for the UK manual that got shipped to me today to get here first. I have a big test on Wednesday evening so I can't work on it anyway.

I had heard that my dad had worked on the Mercury (Redstone?)program while with Chrysler. (That's pretty far removed from the Patriot!)

I'm wondering if it may be an aftermarket equivalent type chain from someone like AMG,Braubus or Renntech,etc that one could assume would be a higher performance chain and therefore more resistant to breakage?I'm going to replace my chain on my 560 SEL (215k) that was changed at 158k and wanted to go that route if it is available...anyone here know if this is even offered to install on MB? Otherwise I'll just go with factory MB chain.:confused:

I'm not thoroughly familiar with which of these V8 models have the double row chain, and which don't. But, if you do not have the double row chain, it can be upgraded to the double row chain to add durability. If yours is already a double row, the important thing is to replace the chain AND guides periodically. The chain itself is usually not the cause of the problem. Once a guide gets brittle and breaks, it typically jams the chain causing it to break. If there is such a thing as a stronger chain, it probably would not prevent breakage in the event of a broken guide.

The safe thing with the V8 is to replace the guides and chain if there is any doubt at all. The sixes and fours are expensive enough to correct chain failure damage, the V8's have astronomical repair bills when this happens. If there is ANY MB engine that warrants timing chain and associated component replacement for preventive maintenance reasons, it is the V8's.

Best of luck,

broken chain and camshaft
 

my 92 500sl lost both on startup at 90000 also bent intake valves on number one

So your cam broke too? I though they were pretty tough to break. MB cams are even tougher. Could this be a metallurgical failure?

Cam breakage is due to the valves being rammed against it when the cam stops because the chain breaks....The valves are open, the piston comes up and BAM, the cam pops.

Right, but I thought that the torsional strength of the cam would be far greater than that of the valves. The valves should bend first as they are already makeing contact with the piston at an angle so that they are not at their strongest.

I just didn't think it could happen that the cam would give first, unless faulty.