Hey Guys...so this is an added to to my '300D 0PSI Compression post'...I finally got a tool from MB Source to pull precombustion chamber, and pulled glow plug on my dead number 5 cylinder. This is from a 300D two owner 160K mile car in perfect shape with all records. I was driving about 70 on the highway when all of a sudden, black smoke out the back.....stopped, and engine was doing a dance...got home, cracked injectors and found the problem with number 5. Make a long story short, compression went to zero, even with a wet test and bleed down. Suck back on tail pipe.Pulled glow plug and pre-combustion chamber...both tips missing and melted away! Hole in piston, you can see the wrist pin! I can't figure this, except to say maybe the waste gate was stuck and the car had excessive boost leading to cooked valve, dropped valve head, and then pieces everywhere! Investigation will continue...pictures of the glow plug, precombustion chamber, fiber optic scope, and good comparison piston attached. Please check your cars so this doesn't happen to you. It so sucks if we lose an engine to something like a rusted gate or malfunctioning overboost circuit. At this point, while the investigation continues, that's all I can think of. A rebuilt engine is $10K these days...OMG...have to find a good used one, and plan on a lot of labor...

Attached Thumbnails

       

WOW! Thanks for the pictures.

Yikes!

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Are you able to test number 5 injector? If it was streaming that may also be the cause.

__________________
92 e300d2.5t
01 e320
05 cdi
85 chev c10

I have seen a VW TDI that did that and the top 1/2 inch of the piston was stuck to the bottom of the head and filling up the exhaust port.

The injector on number 5 alternates between streaming and spraying...pop pressure was 1800 PSI using the Mercedes Source test rig...how would streaming injector lead to high combustion temps? I would have thought that would just be incomplete combustion. If a bed injector can cause engine failure like this we all better change / check injectors asap on any new acquisition! I'm still freaked and bummed this happened. I had a set of Monarks I was prepping to install before this happened...

The streaming fuel causes the combustion to not be even inside the prechamber etc. Not so bad in IDI as in DI (they can really blow holes in pistons).
"Excessive boost" would only cause leaner combustion, although if it really was out of the turbo's efficiency range it would raise combustion temps.

__________________
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

I have personally only seen that kind of damage once. I had a Suzuki 3 cyl, two cycle motor cycle years ago. On this bike, they had an oil collector tube full of small holes that ran the length of the exhaust muffler. This tube needed to be taken out from time to time and cleaned. Well I was doing about 60-70 mph on the highway, when I heard a bang, and the bike started to loose power, but was still running. Bike would not go over 30mph, and I was able to nurse it home. Pulled the cylinder head off, and found that one of the 3 pistons had a hole right in the middle about the size of a half dollar. Inspection of the oil collector tube in the muffler showed that it was clogged, and I surmise that the back pressure in the exhaust system caused the hole in the piston. I installed a new piston, cleaned the oil collector pipe in the exhaust, and the bike was as good as new.

__________________
96 E300d

I'm just so shocked this happened...this is my first diesel and I bought it because of the reputation of the MB diesels, especially the OM617. I wish I could nail down the cause of this...hopefully if there are enough posts, this might help everyone be aware of some major element that has to be paid attention to in order to preclude similar damage to their cars. Sustained highway running at 70-80 should be in the capability of this engine! It amazes me that metal particles got up into the pre-combustion chamber and eroded the glow plug. Then again, it's hard to ascertain what caused what. For example, I've read about glow plugs that have eroded away and maybe that metal entered the combustion chamber, although the pre-combustion chamber holes are pretty small. Debris in the main combustion chamber could always get momentarily caught in the exhaust valve seat, if if the valve doesn't seat, heat transfer is compromised, which could lead to valve failure.But it takes a lot to break off a poppet valve head. Really wish I could figure this out!!

Very uncommon on these engines. It is about the last thing to expect.

If, indeed, the pop pressure was 1800psi, then that should eliminate early injection as a source of the apparent detonation. However, if the nozzle valve leaked, or stuck open during operation, then there would be detonation of the fuel prior to the intended start of combustion. The failure mode of the piston crown is a characteristic detonation failure.

Verify if over boost protection is working then your answer will be clear.

__________________
92 e300d2.5t
01 e320
05 cdi
85 chev c10

Perhaps the tip came off the glow and poked a hole in the piston.

I once had a glow come apart on a 6.2 G M diesel and bent the rod.

__________________
[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

That injector is junk if it's streaming. Pop pressure is only part of the equation, spray pattern is far more important. Streaming/peeing will make the injection event happen at random times or continue dribbling before or after the injection event is supposed to take place. Depending on where it's spraying, it can cut the end off the glow plug, erode the vaporizer ball in the prechamber, or blow holes in the sides of the prechamber. All of the above are documented in various places on this site and elsewhere on the internet.

It's highly unlikely this just "happened", bad injectors give warning that they're failing with excessive noise (nailing/rattling), smoke, poor combustion, shaking at idle, and various other symptoms long before they seize up and wreck your engine or prechamber. At 160K they were probably original and way past the "service now" mileage of ~100K miles.

Creating unnecessary hysteria because an extremely unusual event happened to you doesn't help your cause or your credibility.

__________________
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!)

Does this mean that Injectors should all be rebuilt or replaced? at 100K?

- Peter.

__________________
2021 Chevrolet Spark
Formerly...
2000 GMC Sonoma
1981 240D 4spd stick. 347000 miles. Deceased Feb 14 2021
2002 Kia Rio. Worst crap on four wheels
1981 240D 4spd stick. 389000 miles.
1984 123 200
1979 116 280S
1972 Cadillac Sedan DeVille
1971 108 280S