Gee, we are talking about cars well past their expected lifespan and you are complaining?

Even a simple car is an incredibly complex engineering and manufacturing project, even more amazing is that we can buy one at reasonable cost.

An injector that does not shut off cleanly / dribbles after the injection cycle can melt things. With a failing injector, the flame front occurs at the injector tip / pre chamber rather than in the combustion chamber. Think about a cutting torch directly against metal rather than in free space inside a box.

But hey, diesels never need a tune up right?

Not complaining about older MBs...my most reliable car is a '69 280SL....the car goes and goes...when any of my other cars have a problem, the SL fires up and runs great. I just get disappointed at areas where a bean counter pushes to save a bit here and there. For example, one has to wonder why MB ever moved away from a double roller chain, which was so robust for so many years, to a single row? How many V8s were affected by that move I wonder. The cam problem in the M103 surprised me, because QC should have caught that...all they had to do was section a sampling of cam lodes and after etching, they could see if there was a clear demarcation between ductile and hardened portions. then again, Chrysler once pushed the idea of it being cheaper to have the customer be the QC inspector and have any post production issues addressed by the dealer...this was pre-Iococca days. The 300SE I had was a 78K mile car before the cam started getting sloppy when I had to replace it. Which reminds me...I had to do a water pump on that car once...what a bear! Took me 3 days...it is really buried down there on those engines...and I thought my SL engine compartment was cramped!

It can't be luck! No way a chunk that large missing from the pre chamber tip did not cause major damage in the combustion chamber!

What is the pic of the grain structure from?

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

The pre chamber tip probably didn't come off in one piece, it slowly burned away.

I don't blame MB for prechamber failure I was just wondering what their opinion on it might be.


however soft cams and worn guides on early M103 is on MB but they did correct it and I had a 1986 300E 160k miles and the original cam and rockers were still good so one could argue that it's not that big of a deal anyway.

Do you believe it? I don't. The ball is also gone. Did the ball slowly burn away first before the tip slowly burned away? Let's say if the ball did slowly burn away, did the 2 arms of the ball fall off and also slowly burned away?

He did say he thinks the ball went first and shattered the tip https://youtu.be/JGfIyPwCMRQ?t=99

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

" We no-longer support Windows 3.1 "

LOL, 'we no longer don't support Windows 3.1'!
Yeah, I guess it's getting to be academic. I had no warning of the failure, and it was sudden and dramatic while on the highway. Whatever the cause, I think we can agree the prechamber and that ball and its support are pretty robust. I think someone posted that injectors should be rebuilt/swapped out every 100K...considering the ease and low cost of doing so, I think that's a good idea, along with the glow plugs. One or the other or both were most likely the cause here for the catastrophic failure. Oh, someone asked about the grain structure...that was of the sectioned prechamber. On another topic, today I worked on smoothing out my idle on the replacement 617 engine...took a shot at the rack damper bolt...wow...what a difference...it idles beautifully with no bounce...must have dialed it in about three turns...probably could use the new style with stiffer spring which I ordered...but for now, it surprised me how well it adjusted. No problem stopping or starting either.

I'm no metallurgist. Care to tell what the grain structure pic is trying to show? What magnification and what took the pic?

You called it Stainless. I think it is made of something much tougher. Probably Inconel.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

I'm no metallurgist. Care to tell what the grain structure pic is trying to show? What magnification and what took the pic?

You called it Stainless. I think it is made of something much tougher. Probably Inconel.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Funola...that is of stainless, taken in my lab...actually a lot of pics taken of different metal parts involved in the failure...there were dislocations near the tip, leading me to feel the tip was expanded due to being blown off. I see you had a 300D with just under 300K miles...you stated it ran great...what mileage did you buy it at? I'd be interested to know how you took care of it...oil change intervals, valve adjustments, injectors, etc. Appreciate any info...thanks!

Nice to have a lab at your disposal! The pic is of the blown tip of the pre chamber and you have determined it to be made from stainless? What alloy stainless? Without knowing anything in the trade, my guess: the simplest test w/o sophisticated equipment would be to check it's melting point to determine what alloy it is.

My 83 300D was my first Mercedes. It had around 200k miles and a rebuilt transmission (with receipt) when I bought it. It was slow and had gray smoke in the exhaust. I changed the oil and filters and gave it a lot of Italian tune-ups which transformed it to be a great running engine. I then converted it to run on a 3 tank veg oil system and put about 100K miles on it with no engine related problems. Engine still starts and runs great when I removed the veg system and sold it (due to rust) to a forum member (with full disclosure) who was going to put the engine into a van conversion. That engine had 500 psi compression on all cylinders at the time it was sold. I changed oil at 5k mi intervals with 5W40. That was a great car and served me well.

Edit: I did rebuild and pop test the injectors with Monark nozzles.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Yes, good to have a lab...used a desktop SEM, Hitachi TM-1000 and an optical...but we're not metallurgical...I don't know what metal it is....I'm passing the material to a colleague at Uconn in material science to answer that and other questions free of charge. We do do gov't applied research...called BIR...Small Business Innovation Research...special govt set-asides for small biz alone.

Your car sounds amazing...500PSI on the cylinders?? Stunning...must have had a lot of power. Good to know that if well maintained, these engines can go the distance. Sounds like you had great luck rebuilding your injectors...the first couple of times I tried with Monark cores, the body leaked/weeped in the middle...I had to do a lot of lapping to fix that...wouldn't show up on the bench, only in a running car after a few miles.

Do you agree doing injectors and glow plugs every 100K or so? It seems to be that way. What oil make did you use? I've ben using Shell Rotunda with a bit of Liquid Moly.

Sorry, I got the compression #'s mixed up with my Jetta diesel that had 500 psi compression on all 4 when last checked. The 83 300D had 420 psi at around 290K per this thread My compression test results = good on all but #1 which had 400 psi.

Jetta also runs on a 3 tank system and still starts and runs great. It probably is at around 270K with about 60k on veg. This reminds me to do a compression test on the Jetta soon, also pull the injectors (with Monark nozzles) to inspect and pop test them.

Here's a video from 2011 https://www.youtube.com/watch?v=a5AB-Es6MZk of a compression test on one cyl of my 83 300D in under 60 seconds!

The glow plug is already out. Video shows me installing a HF compression tester's glow plug adapter modified with with a quick push on connector, then plugging the 1/8 nylon line into it before cranking. The starter sounds weak. If it cranked faster, the # would probably be higher. At 320 psi, it was probably a cold compression test.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

Wouldn't hurt to do injectors and glow plugs every 100K. Another thing you can do is pull the injectors and pop test for correct pressure, check spray pattern, and no peeing every 25K. Do the same with glow plugs to inspect and power them up. If they look good, I put them back in.

Did you torque the injector halves to spec? Was the injectors rusty inside? That may have been why they leaked and required lapping.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked