86 560SEL what happened?? :(
 

My 86 560SEL w/ 64K miles was running smooth as silk. Was sitting or a few days. Went out to drive it, started it up and it sounded terrible. Made loud knocking sounds but ran smooth, oil pressure gauge all the way up at 3 bars. I turned it off and now it won't even turn over!! Turn the key, everything lights up, turn key to start and just a hear a clunk. I've had a little trouble with the neutral safety switch, but could always jiggle the shifter and get it to start.

I'm worried the engine locked up from the terrible clunking sounds when I started it before.

Haven't gotten it to a mechanic yet. Obviously will need towed.

How could an engine that was so smooth and quiet just all of a sudden make such knocking sounds?

Could it be something simple or should prepare for the worst?

Sounds like the timing chain ate a plastic rail guide and then the chain jumped out of time and the valves hit the pistons. A standard way of failure for these engines. Expensive to fix at this point.

If that were the case, would it still run? The car started up fine and I let it run for a couple minutes. It didn't run rough, just made a loud knocking sound. Engine wasn't shaking or anything like that.

I think your going to find out that your 560 didn't have 64K on the clock. Have you tried turing the motor over by hand?

It checked out with autocheck.com when I bought it with 53K. Also, service stickers and books would support the mileage represented.

Did you inspect the engine for visible damage?

T- chain will sometimes knock a hole in the valve cover.

Perhaps an ancillary component failed- belt or pulley?

Nothing appears amiss.

here's an account of exactly what happened...

i got in the car, turned the key and started engine. shifted into reverse. HMMM... engine sounds different. shifted back into park. opened door. WTH?? sounds like a really bad valve tap but more clunky than that. opened the hood. car still running. everything looks ok. got back into the car. pressed gas to speed it up just a little, like maybe 2500rpm. still same sound. hmmmm... i better turn it off. turned engine off. tried to restart. turn key, just hear click. wiggle shifter cause i've had it not start a couple times cause it didn't seem to be in park correctly. just hear click. thought, oh f...

got into my trusty 85 300SD w/ 238K and went to office

560 sitting in the same place since then

From the limited description, IE not being present, it sounds like it jumped time.

The rails are plastic and should be replaced every 10 years regardless of mileage.

I'd remove the valve covers and take a look.

a mechanic friend who works on mercedes came by today. he wasn't able to turn the engine by grabbing the belts and turning. said that doesn't necessarily mean the engine is locked but he is usually able to turn an engine that way.

what's the chance if my timing chain has slipped that the engine ISN'T trashed??

rsmartin said: what's the chance if my timing chain has slipped that the engine ISN'T trashed??
_______________________________________________________________
Two chances...... slim and none. And Slim just left town.

You might get away with just doing the heads.

That was my first thought also, the plastic rail guide disintegrated or broke.

It ought not to have happened at just 64,000 miles, but then 21 years without having had it changed is a LOOOOOONG time on the original one.

Mileage and time causes the original ones which are white, to become root beer brown, and over time and mileage they develop hairline or big cracks, and eventually they let go. There is no set way to tell, on the 560, it varies engine to engine, but the best bet is to change them along with the chain and tensioner at 100,000 miles (typically driven in 10-12 years)

Yikes
My mechanic says wait for the rattle

Not feeling very comfortable here...

:eek:

If you "wait for the rattle" you are really taking a chance...many times "the rattle" is the first and last thing you will hear as the chain jumps time and the carnage begins inside the engine. 10 years and/or 100K miles...when you hit those numbers it is time for a new chain, tensioner, guides, etc.

If money is an issue, yeah just wait for the rattle then you have to change it. It could last for a few more years.

If you have the money I'd do it right away, since chances are they are original...

what about my 84 300SD w/ 210K and my 85 300SD w/ 240K? do they have the same issue?? are u saying i need to have them torn down to have the chain, tensioner and guides replaced as well?

On the 617 its a good idea to check the chain for stretch but they usualy don't break. After 300k miles it probably would be a good idea to roll a new chain on to regain performance.

Overhead cam V8's have very long chains, two sometimes four actualy, inline engines don't.

91 420SEL LH Cam jumped time, bent exhaust valves. What's the cause?
 

I bought a 91 420SEL a few years back and gave it to my son to use while he was going to law school. It had 200,000 miles on it and the timing chain had never been replaced so I order the parts and was waiting to take it into an independent shop to effect the change.

Before it was done, the car was driven by my wife (a school teacher, no less) and she returned it to the garage. It sat for a couple of days before I tried to start it and it wouldn't. It turned out that the LH exhaust valves bent on the startup attempt and it seemed to conform to that described elsewhere in this thread. I pulled both valve covers and found the inner upper chain guide on the LH side broken and the exhaust valve rockers out of contact with the cam. There was no damage to the RH side.

The timing chain, tensioner and upper guide rails were replaced and the LH head reworked by an independent shop. The car ran perfectly for 15,000 miles. Then it failed to start when my son ran into a bank for 15 minutes. After it was towed to a local MBenz dealer, the failure was determined to be the ignition control module (by substitution) and it was replaced with a used one from eBay.

Two weeks later the 420 failed again while running. The failure occurred while running at moderate acceleration (34-40mph) with the engine warm. A clunk was hear, the engine began to lose power and it stopped completely and would not start. This time, I had it towed to my home. After checking the obvious, I pulled the LH valve cover and found the exhaust valves not returning with the rockers dropped off for the exhaust valves. I also saw a small chard of plastic (about 3/8" polygon) on the ledge of the chain cavity and took a picture of it.

Could one of the new guides have fractured? Or, could a piece of the old guide rail been left in the engine? With a mirror and light, I could see no evidence of any missing parts or damage to the new upper chain guides. I called the independent shop, got sympathy, but no plausible explanation of what could have happened.

Over Thanksgiving weekend, I disassembled the top end of the engine. The timing chain guides were indeed intact, the timing chain was still in mesh. I turned the engine to TDC using a socket on the crank. The RH cam was in time, but the LH was off, late about 12-15 degrees (the tower mark on the left cam tower is somewhat ambiguous). The LH cam had indeed jumped time as suspected. I checked the distributor rotor position as well and it was in time.

Why? I removed all three plastic rails. They were in perfect condition. I removed the hydraulic tensioner and rail. The plastic tensioning rail, too, was in perfect condition. In fact, everything that had been renewed a year and a half earlier was in perfect condition and installed properly. I removed the LH head to have a valve job done on it. But, the problem of why it occurred keeps nagging me and I began to remember the admonition of the definition of insanity. So I went to this website.

I've read the speculative posts, most of which don't make sense to me. The lack of oil pressure on start up doesn't apply here because it failed the 2nd time while the engine was running. Besides, what engine designer in his right mind would rely on holding hydraulic pressure through a check valve for extended periods to avoid catastrophic engine (interference) damage? Too, the tensioner is preloaded with a mechanical spring and this failure wasn't at start up, but at moderate running speed. (I noted that Mercedes has increased the mechanical tension on the replacement hydraulic tensioner such that a longer bolt has to be temporarily used to draw it up). Worn sprockets? No evidence at all. Brand name disloyalty which should be punished? No, replacement tensioner supposedly was Mercedes; likewise for chain and plastic upper guides. Low oil? No, it was recently changed and was less than a half-quart low. Failure of the oil pump? Could be, but it would most likely be catastrophic, not intermittent; dropping the pan shows no apparent problem with the pump or the oil pump chain.

Improper repair? Well, there was some evidence of some minor things done poorly like two o-rings in an injector holder due to improperly cleaning the old one out of the cavity, but nothing material to the fault of jumping time. The car passed emission tests shortly after the first repair and subsequently without problems. However, I don't know that the engine was in perfect time after the repair, but I doubt that it was marginal.

This timing chain problem with the 420/560 discussed herein has far too many instances for anyone to have found the true cause and it seems endemic to this engine design. (I have a 76 MBenz that has over a million miles with the same time chain; likewise a 300TD with 375K miles with the same timing chain and I have never had a GM engine timing chain fail. Replacing a double-row steel timing chain every 100,000 miles as preventive care sounds ludicrous, because it is. Speculation about oil check valves preventing chain slap on start up may be true, but if it is so, the engine designer should be shot. I suspect something else is going on that preconditions this engine for timing failure on startup or while running. At least in the instant case, I know it is not "chain stretch" or "broken chain guides" or "worn sprockets" or the other transplant diagnostic, whip-the-messenger-boy catchalls.

As coach Bear Bryant remarked, there's just too many failures on this side of the field.

Why just the LH side? It's the first in the series, for sure. But if it were due to a worn crankshaft sprocket (which has one half the diameter sprocket of the cams, thus less teeth in contact, and would be the first sprocket to encounter a slack loop upon failure of they hydraulic tensioner), all three (LH cam, RH cam and distributor) would slip time - not just the LH side. There was no evidence of bearing seizure on the LH cam or towers and the cam turned freely as it should.

Now, I have no reason to advance this new conjecture other than that the others fail to satisfy the instant case fault phenomenon, but here goes: What if the so-called timing chain/guide "failure" was a symptom rather than a cause? No post that I have seen in the past two or three years offers anything but speculation about how this failure actually occurs. I did see some pictures on one site whereby a reconstruction of the broken guide could run under the LH cam and act like a broom handle in a bicycle chain. But has anyone been able to reconstruct simulation of this catastrophic failure?

The theory that a piece of a broken rail is carried up over the top of LH sprocket works against gravity since it would be on the inside, not the outside, of the chain. The break of the tip of the LH inner chain guide is plausible, but such was surely not the instant case. Besides, this instance does not have any damage to the upper LH guides, inner or outer. So how did it slip time on the LH side and leave the intermediate mechanism of the failure intact?

I've looked into the dynamics of chain design and it may be ignition related. The load on the chain varies (pulsates) as it pushes down the valve springs and it reacts to change in load. I'd like to see a strobed picture of a chain running under load whereby the ignition is interrupted to see if failure could be simulated. (Bear in mind, the MB inline diesels, which use mechanical injection and have no immediate shutdown, don't have this problem, though they use the same type of hydraulic tensioner and chain. Sure, chain "stretch" will affect diesel valve and injection timing, but they don't have any where near the incidence of catastrophic "chain failure" of the 420/560 gas engines. Could it be that such an event as an abrupt ignition cut off creates a "traveling wave" that presents a whiplash loop that invites the first loaded cam to skip a tooth and/or also breaks the plastic guide rail (if it's embrittled with age)?

This engine ran for 200,000 miles on the original chain, so why did it fail with only 15,000 miles on renewed OEM parts? What could the repair shop have done wrong (or failed to do) that could have caused this second failure? What quantifiable specification was violated?

I'm going to take off the front cover and take photos while I'm doing it to see if I can forensically determine the cause, but would appreciate any insight those that have been there may have.

I have seen a few of these problems on 420s and 500 engins. I have never seen a broken chain but have seen broken cams and cam towers and many bent valves on the left head. In every 6 cases I have seen, there was at least 1 broken guide. I believe when you pull the front cover you will find that one of the lower guides is broken. I personally believe that when a chain jumps timming that the front cover and oil pan need to come off and all guides replaced. I think that part of the problem is that the chain changes direction so many times, the load is constantly changing and the chain starts to vibrate and fractures an old guide which causes all the problems. I will agree that the chain is the weak link in the V8 engins but with proper maintaince, they will last forever.

This timing chain problem with the 420/560 discussed herein has far too many instances for anyone to have found the true cause and it seems endemic to this engine design. (I have a 76 MBenz that has over a million miles with the same time chain;
_________________________________________________________________
I don't recall ever seeing any posts on this site saying that the chain broke. It is always the plastic parts that cause the problem. That being said, why would MB design an engine using plastic in the timing system? This is a huge problem just waiting to happen. I grew up driving and racing GM vehicles and never saw a timing chain problem on any street car. Only at the drag strip with highly modified V-8 engines did chain failure ever occur. When I begin driving MBs I was told about the 10 year/100,000 mile rule. I couldn't believe what I was hearing. Again, why would any car manufacturer design an engine with plastic parts in the timing system?

You can't compare a GM V8 to a MB. The MB engines are overhead cam so the chains are much, much longer, most of the new engines are quad cam so thats even more complex.

On a GM V8, like the 5.7 the cam is in the center of the cylinders, so the timing chaid is very short. Their are no guides or tensioners to wear out.


Different design's you can't compare them.

Plastic guides and rails are used to keep the engine quite, and they last a very long time. Even the metal ones wear.

Plastic guides and rails are used to keep the engine quiet, and they last a very long time.
_____________________________________________________________
I don't consider 10 years or 100,000 miles a "very long time" when you are talking about an MB. People used to buy these cars because they were built to last. If the main engine can run for 300,000 plus miles without any major overhauls then the timing chain and parts should also last that long. To me the timing chain and related equipment is not a service item like brakes and filters, etc.

I still own an '86 560 SEL and had the timing parts replaced at 10 years/100K miles and I am going to continue to drive this car until it stops running with no more replacements for timing pieces. MB is losing the long haul buyers. The newer models are just not made to last as the older ones were. And MB is probably correct in their marketing. Many folks today won't drive the same car for 5 years, let along 10 or 20 years. So they could care less about long lasting durability. They buy a new model and dump it when the warranty expires. As they say, if you are buying a used late model MB be sure to get the longest factory warranty you can buy.....you will need it. The main reason that the newer used MBs are so cheap compared to years past is that people know they are going to have to spend a lot of money just to keep the car on the road. An '86 560 SEL in 1996 was selling used for around $22K. Now in 2007 you can buy a used 1997 S500 for $12K. The 1986 model sold new for around $55K, the 1997 model sold new for around $75K as I recall. Do the math. The used '97 is much cheaper for a ten year old car than the '86 was at ten years of age. And if you consider the difference with inflation it makes the '97 model worth even less compared to the '86 at ten years of age.

What model?

Seems from reading these boards that for every m117 failure, there are 20 m116 (420) failures.

Never hear much about 450 or m100 t chain failures. or at least i don't.

300SD million plus
 

[QUOTE=fahrgewehr2;1686557]What model?

300SD, Stuttgart edition, special order with leather seats.

1976 300sd?

Oops, 300D
 

Don't know how the "S" got in there.

It's a 300D, naturally aspirated.

That chain was really the only major downfall of the V8 engines in the W126 models, even the 380SE model. That was exactly why I sold my 1985 380SE. I loved the car, but the date/mileage of the last timing chain/tensioner/rails/guides was unknown, so I sold it. It was too old and had too many miles to sink hundreds of dollars into for this repair, especially since I had developed an occasional stalling, which I was informed was bad injector seals.

Too bad MB did not make these "non-interference" engines, or have designed the engine to have not had the "crumbly with age" rails. I think alot of that junk could have been eliminated. Take Lexus for instance... from 1990-97, the 4.0L V8 was a non-interference engine. If the timing belt was to break, no engine damage would occur. I had a 90' LS400 with 252K and AFAIK, it still had the original timing belt - engine was still super smooth and quiet and very powerful. I would have to look down @ the tach to see if the engine was still running, it was so quiet.

However, in 1998, they (Lexus) switched to a VVt-i engine, which was an interference engine, as was the 4.7L V8 in my old Toyota Tundra truck. Why they did that, I have no idea. I mean, why unnecessarily add risk of major engine damage if its not necessary?

To the guy that also has the SD models... unfortunately, from what I have heard, these cars have interference engines as well. If something in there breaks, the engine is likely ruined.

Good luck!

m110 owners don't defer maintenance. Ever.
And as for the cast-iron block 3.5 and 4.5's, the early ones had aluminum-backed rails. Mine has 145k on the original rails and I will NOT ever replace them at this rate. MAYBE I will have them professionally recoated, but they will not snap unlike the plastic ones.

Yeah well go buy a BMW or a Jag and you will run into the same problem. Its an overhead cam V8 and V12 thing. Go take a look at what the chain on that kind of engine looks like and how it is run compared to your old GM V8's, it will become clear.

Inflation adjusted my 300SDL costs about what an S320CDI would go for.

I'm the orginal poster of this thread.....

Well it's been 5 months and finally my mechanic has decided to look into the "dead" 560SEL. He's a diesel guy and really dislikes the "gassers" but yesterday he decided to have a look. Here's what we found.

He dropped the oil pan first to see if any pieces in there. Crystal clean.

So off come the valve covers. Upper chain rails have NO discernable wear.

The cams are still in alignment, so it appears no chain jump.

BUT the hydraulic tensioner is soft and does not hold the chain tight.

I'll try to explain what happens as best I can...

If he turns the left cam slightly to take some slack out of the chain he can turn the main crank maybe 15 degrees until it binds. if you turn the left cam backwards you bring everything back to where it was again... so you can only turn the engine maybe 15 degrees back and forth... make any sense?

so we can only surmise that a lower guide has broken and has jammed something up?

but since the cams are not out of alignment with each other or with the distributor, it seems that there shouldn't have been any valve damage??

you see i'm trying to see if anyone can give me any reason NOT to do a complete upper end overhaul, i.e. pull the heads, valve job, replace chain, tensioner and guides, etc.

at 64K miles, doing all that would basically give me a new engine, right?

what you all think i should do?

You really need to find out if the cams ARE aligned right and, honestly, the only way to tell is if the engine is at TDC for the #1 cyl and the notches on both cams line up with the towers. You can't really tell otherwise, because 20° at the crank is 10° on the cam and it's really hard to tell 10° of cam movement, and that's exactly 1 tooth.

The engine's being bound up, and unless you take the heads off you can't tell if there is piston damage but if the engine's being bound, you'll need at least 1 valve, even if it's just from the starter. The flywheel alone weighs enough that 100RPMs of momentum on it would seriously bend a valve. Make it your own DIY project. Take the heads off. I did heads on my 4.5 (an m117) in 1 weekend, with no prior experience, and I bet you could at least pull them off yourself to see what kind of damage is done. Find a used replacement head at a pick-and-pull junkyard for $50 or so, have the stems and seals replaced on that one and the other presumably still good side, and you're set until 200k at least.

everything was lined up at top dead center ... but come to think of it, why would the engine lock at top dead center on #1 cylinder. I saw the marks lined up on the cams and towers myself. but what would cause the engine to stop right at top dead center.

i don't have the time or tools to do it myself.... i'll spend the bucks if i really need to. my mechanic said the same thing as you... hard to believe that there isn't a bent valve due to trying to start it.

With only 64k on it I'd probably have the engine repaired and then enjoy it another 150k.

Answer:
 

If all the plugs are removed, and it still locks = bent valves.

Caused by the bad chain tensioner.:(

An interesting post, a few points:

1. Every GM small-block V8 (including some Hi-Po) I've seen had nylon on the cam gears from the factory. Of course, you could use that timing chain as a collar for a big dog...

2. I've read that recently-made MB tensioners have an extra valve to prevent leakdown, whereas other mfr's (Febi, for example) may not. I don't know if this is true but if it is my next preventative tensioner replacement on my cars will be genuine MB; I'll look at the price difference as catastrophic insurance.

3. An unexplored area on timing failure is the possibility of a binding camshaft from bearing misalignment or lack of oil to the bearings. When I replaced my 380's camshaft I was amazed at the high-precision fit in this area. Even the smallest unmeasurable (with my tools) misalignment caused binding. The final adjustments were made with a plastic mallet and some patience before final torquing and spin testing. Even a little binding can cause a dry spot on the bearing and eventual heating/wear, etc. If a cam binds, something is going to slip or break at the weakest point, and those points on these engines are made of plastic.

4. I don't think that there is a way to make an old-school "hi-perf" 2 valve per cylinder engine that is non-interference, because of compression and valve lift requirements.

Based upon your data, I would imagine that the chain isn't the issue. I will say that I have never seen valves keep a motor from turning with the starter. The starter will just bend them if they aren't closed.

I'm guessing that something has fallen into the motor, probably on #1 or #6 as that is why it stopped with the piston at the top.

As to chain issues, my shop has repaired hundreds of them on all versions of the 116 and 117 motors. A couple points of interest: there are only two rails that actually touch the chain when rolling in tention. They are the tentioner rail and the rail below it on the lower right side of the motor. The rails that cause all the problems are the three in the heads and I recommend them to be replaced every 75k or 5 years whichever comes first. They are dirt cheap but do take a few hours of labor to replace. If you DIY then it is cheap insurance. I see no point in any other level of preventative maintenance except maybe a new chain every 200-250k miles.

We just burried my all time mileage test case this week. It was a 90 420SEL that had 950,000 miles. Something finally gave in the lower end. We had done two chain jobs on that motor the last one over 450,000 miles ago. We replaced those rails almost every year as he drove 90,000 a year.

i called my mechanic and clarified a point. the engine was not stopped at top dead center. he was able to turn it to TDC by turning the crank, then turning the cam to unbind the chain, then turn the crank, then the cam, etc. so something is causing the chain to bind down low where we can't see. again, no debris was found in the oil pan.

i have a snake light with a camera attached. i think we'll try to look up from the bottom with the snake light camera and see what we see

but if you were me.... how would you proceed?

i'm thinking dive into the front first, taking off the chain cover and see what we find... replace chain and all guides since we're there already. assuming we find a problem .. say a broken guide down in the lower part of the chain area (not very good at the technical language) would you just go ahead and do the heads and valves as well? my mechanic (who is mainly a diesel guy - i have and 84 and 85 300SD) is thinking we just go for it and hopefully end up with a basically renewed engine that will go for the next decade.

i don't want to spend the thousands of dollars if not necessary but don't want to be penny wise and pound foolish.

here's picture of the car if anyone cares...

While the starter is strong enough to run right through interfering valves, turning it by hand won't be. I would remove all the rocker arms so the valves will be closed and see if you can turn the motor. The rockers won't be removable on valves that are being depressed so you might have to back the motor up to get all of them.

:eek: Save it!! That is a BEAUTIFUL car!! Wow...its so flawlessly clean! That car has a looooong life ahead of it!

What Steve said. Remove the rockers. I would also measure the hight of each valve and look for one or more that are shorter than the others. If they are all the same, you don't have any bent valves. At least you will know one way or the other.
By the way, I would sure fix it or sell it to me.

A dislodged valve seat can cause similar symptoms.

Check out this thread for information; "Exhaust valve for #4 cylinder sticks open about a 1/4 inch in 1987 MB 560 SEL".

Links to thread-- http://www.peachparts.com/shopforum/showthread.php?t=208049 AND http://www.benzworld.org/forums/w126-s-se-sec-sel-sd-sdl-class/1352311-exhaust-valve-4-cylinder-sticks-open-about-1-4-inch-1987-mb-560-sel-engine.html