At a minimum they should be pop-tested and pattern-tested and shimmed if necessary. If worn with poor pattern, they should be replaced.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I had the same thing happen on my 85sd 617 motor I lost #4 cyl. while traveling about 75 mph. on a 1400 mile trip about 500 miles into it blew the bottom of the prechamber down into piston made a bad rapping noise and had a loss of power. Well made it another 200 miles to my destination and was told I should be able to make it 700 miles home if I keep it under 65 mph and baby it well I did make it 699 miles back and had to tow it the last mile. The only thing that I can think that happened is about 300 miles before I went on trip I decided to do some prematainence on my injectors so I totally took them apart cleaned them with a sonic cleaner pop tested shimmed and balanced them and ran it immediately it did not sound right kind of like nailing but it ran good and was good on fuel well one member told me I should not have taken the injectors so totally apart that is probably what damaged the one I guess it was from my stupidity that I blew the engine still setting on my garage floor guess you live and learn have to be very careful when messing with injectors wish I would never have touched them got another engine from a member on this site and running it today yet as my everyday driver on wvo with about 365,000 currently so yes a bad or out of adjustment injector can toast your engine along with losing an oil cooler hose, or vaccum pump 3 main issues of losing a 617 I lost 2. On a Sprinter engine they have a thing called black death which is a leaking injector that causes lots of engine failures. Yes try to find a good engine and swap it out, Currently there is I think 85 300SD on Ebay with 5,500 original miles asking $50,000 for it I think it cost around $42,000 back in the day maybe you want a 617 in like new condition all the way around.

When these cars were new,nozzles warranty was a 100,000 miles.
Here was the real truth,if more than two nozzles failed after cleaning
no warranty would be given! Seldom did any one get free nozzles.
Who came up with this 100,000 mi. rule that nozzles would last this long.
The nozzle pintal may go up and down this many miles but does not mean it
would pass testing.
I personally clean and reset my nozzles about once a year. Normal find
one or two need to be reset.Drive normal ten thousand miles year,
usually easy driving.
Could nozzles last this long (yes) with proper maintenance,Usually does not
happen.
Poor fuel,water in fuel and others can destroy nozzles.
When to check nozzles,loss of power,rapping clattering,missing at any time.

Judging from the pics, this is what I surmised.


Some of the other more exotic explanations don't seem likely given the history of these engines.

__________________
-Typos courtesy of my mobile phone.

Well for that explanation to work, the glow plug tip has to smash the bottom off the prechamber to get to the piston...and that prechamber looks melted not like something that's had a piece of metal hammer at it. Not to mention the lack of knocking noise.

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

Well, it was not as one member put for me to appear as an alarmist, I just wanted to get this event out there so one else has it happen to them. As I indicated in an earlier post, this is my first diesel, and in my first year of owning the car, I've been doing maintenance items everywhere, from new trans, to entire front end, to vacuum, and finally did a diesel purge. My next on the list was the injectors. They have not been nailing and the engine would idle nice most of the time. One cannot do everything all at once, or we'll all be rebuilding a car from ground up. I was hoping to solicit some insight and shared experiences with others to answer what exactly happened here, and what we as owners should do preemptively ASAP when buying another diesel. I find it highly suspect that a jet of fluid at 1800 PSI could erode enough stainless of the pre-combustion chamber to do this. The valves in these engines are sodium filled, which creates a heat pipe to heat transfer combustion heat away by conduction when the valve is seated. A burned valve u8sually happens when some debris gets caught in the seat and/or the seat burns first, causing a narrow opening and accelerated gas velocity, which tends to accelerate the burning and so on in a positive feedback way until complete valve failure transpires.

One possibility I am now considering is that this all may have started with a bad glow plug. These things really do glow bright red, almost white sucking 25+ amps, which means some of these puppies in some diesels are at like 1000C! Though designed for hash conditions, the quenching effect of a direct spray verses a nebulized injector release, might, and I say might because I have not determined the metallurgy here, work harden the glow plug case. Hardened surfaces verses ductile are more brittle, so given the rapid pressure rise in a diesel or detonation condition, could have fractured the glow plug tip and sent metal fragments flying. However, since I the pre-combustion chamber gas holes are like 0.1" in diameter (this from a memory guesstimate), I am struggling with the metal bits being small enough to get through those holes to do much other damage other than a freak situation with an exhaust valve attempting to seat. The car was runni9ng on the highway for only about 5 minutes when the failure happened, so I would not have thought this long enough to eat away the end of the pre-ignition chamber. Until I get the head off, I won't be able to ascertain more what preceded what. What is sure is that given the low cost and ease of replacement, I think replacing the glow plugs, and then as soon as practical, checking injectors after buying a car should be first order of business. I had assumed that if an engine was running seasonably well, there was no urgency, but then never having owned a diesel before, I had no frame of reference as to what running 'reasonably' was, other than viewing a Youtube video. I have since seen pics of glow plugs that have mushroomed out at the tip, making removal difficult, this being the result of thousands of heating cycles causing metal fatigue.

Thank you for trying to help others. Concerning the glow plug and pre-chamber problems-Mercedes Benz states a poor spraying injector can cause the following conditions: burned out glow plug, dispersion ball burned away, pre-chamber end burned open. If we lack experience to know, would it not be helpful to use the expert knowledge of others? Or is guesstimating the way to go? You admit yourself that you are new to diesels, not that it was your fault but these conditions were preexisting (already starting) before you bought the car. Because of a lack of knowledge and understanding how these cars sound or should run, these conditions can be missed. Welcome to the learning curve. Happens to us all. Sorry for your problems and welcome to the forum.

The title, panic, and frantic nature of your postings certainly indicate alarmist tendencies. If you aren't meaning to appear that way, please calm down! We'll get you through this.

If the injectors are good and the engine is healthy, it will idle nice ALL of the time. Clues you have injector problems are rocking idle, smoke at startup or when cold, excessive smoke when pulling away from a stop, uneven diesel "chatter", knocking or nailing noises, or any sort of "missing" feeling at idle or any other RPM range.

Every car is different. What needs to be done ASAP is usually done on a case-by-case basis. A good rule of thumb is fluids and filters immediately if no record of it being done in the recent past. Valve adjustment and Injectors are usually next on the list and high priority.

You'd be surprised what that jet of fluid can do to your prechambers or your glow plugs. As "hercules" posted above, even MB says that poor spray pattern can wreck the glow plug, vaporizer ball, or prechamber.

Stop referring to this as a burned valve. That isn't what happened here. You had a catastrophic failure of the prechamber.

The pieces of slag from the glow plug or vaporizer ball clog the exit holes in the prechamber and create enough back pressure that the tip of the prechamber blows off.

Quality glow plugs such as Bosch or Beru simply burn out after tens of thousands of miles. Mushrooming or bulging tips are typically poor quality plugs like Autolite.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I appreciated the feedback. Not having all tools at hand and being faced with a having to consider how to afford a $10K rebuilt engine certainly caused me to be looking for some explanation of a crazy event. I think 'Diseasel 300' hit it the explanation on what happened. I absolutely think he is right that either incomplete combustion/and/or failed/desintegrating glow plug clogged the pre-chamber holes. It would only take one charge to be lit off to cause excessive pressure to blow off the tip of the pre-chamber, and after that it was all over with all those pieces flying around in the cylinder-piston-head environment. Thank you for mentioning that...in retrospect, I would imagine it would make sense to check any new acquisition injectors of have someone check if they don't have the tools to see the spray and pop pressure, but also, pop a scope down and look at the prechamber to get an idea if there is any degradation or if the holes are plugged, which could foretell a major problem. Makes me wonder why more holes are not in the prechamber to allow gas to escape...must have been some empirical test by MB years back to allow a certain pressure rise time...

I just took some new close up pics of the tip of the precombustion chamber. If you'll note, the sintered/rough look of the tip surface clearly indicates a fracture break. Cast iron breaks with a surface texture like this. This is stainless. Plugged chamber holes could easily cause the tip to blow off, as 'Diseasel 300' suggested. If you look at one of the other shots, you can also clearly see a 'dent' near one chamber hole, this from the outside, so something nailed that while rattling around in the cylinder. It has a point to it so it was a narrow missile of some kind. If the failure were do to excessive temperature, the surface of the chamber would have been melted or smoother that what we see.

Attached Thumbnails

     

The pre cups don't have enough oxygen/area to flame cut the bottom out like that.The idi cups job is to not allow the injection event to expand instantly..but to slowly allow expansion due to limited oxygen in a given amount of space.The hole in the cup determine expansion rate..because really our inj pumps are not much more than a glorified power washer pump. Your pre combustion chamber was breached before it took the Piston. you can clearly look at that piston and see that injector was spraying in a 5 pattern.more than likely you experienced a fracture which eventually failed and allowed the pattern of the injector to spray directly into/onto the crown of the piston. it is also likely that a bad injector could pinpoint the cup causing a fracture and eventually catastrophic failure.Secondly,brand new OM 617 in the crate never fired are $3,500 all day long through IronPlanet. The military has a lot of them because they are used in the hugglands(spelling)which are a tracked off-road vehicle used for snowy icy conditions. They come up for bid quite often. Our family has bought many trucks/engines and parts and all were exactly as described. After reading this thread I haven't even been starting our 300 until I get new injectors in.

That almost looks like gasoline ran through it.

I'm the only one who drove the car...no gasoline in the tank, just diesel.

In my opinion, a bad injector is the cause of the issue here. When it was streaming instead of spraying, the stream of fuel burned off the end of the glow plug, potentially burned through the ball pin, burned through the end of the pre-chamber, and then holed the piston.

Lesson: injectors should be high on the list of items to address.

__________________
Respectfully,
/s/
M. Dillon
'87 124.193 (300TD) "White Whale", ~392k miles, 3.5l IP fitted
'95 124.131 (E300) "Sapphire", 380k miles
'73 Balboa 20 "Sanctification"
Charleston SC

This thread, and the earlier one by the OP,

300D 0PSI Compression No.5 after highway run…Head gasket, burned valve, worse?

should be read with a bit of skepticism; the OP claims both a holed piston, and simultaneously claims no unusual blowby, nor oil smoke from exhaust. Those claims are not consistent.