Pre chamber tips cleaned real easy with a brass brush. The rest of the head and block took a bit of scrapping though. I used a little wire wheel on the piston to avoid gringer grit. It didn't seem very different in height from the third.

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'83 300D turbo diesel (334k daily commuter)
SOLD '80 240D 4 speed manual, #2 piston pitted from crushing a 10mm nut. Running it 'till it burns through.
'78 F-150 300cid 4spd od (with my great unkle's original sales receipt)
SOLD '66 Ford P-350 delivery truck (almost driveable)
'49 Dodge B1D (1 ton Pilothouse era truck) not running but all there, candidate for om617 and 4x4 conversion when money permits.

To measure the distance of protrusion you will need a dial gauge and a (magnetic) stand or a depth gauge - Mk1 eye ball isn't really a great tool for this.

That's a nasty chunk out of the piston.

Nasty things could happen - it could get worse - I guess it all depends on whether making things better is important or not

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

I once had a similar problem with our 85 turbo. Air cleaner nut was dropped into the air intake and eventually into turbo which disintegrated into engine. Engine still ran, but with alarming noise.

Bought a used low mileage engine and had it rebuilt. $7000 all-in for shop & parts in 2001. Still have car and engine runs great - about 100k km on rebuild.

Not worth it unless you can do most of work yourself.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Sure they can but it sounds as if he bought the car with the idea that the engine was toast to begin with so a little experimentation under those circumstances might be educational. Will it last 1000 miles or 100k miles? Seems to me that the most likely thing to happen is that the piston becomes holed. If so, it's not really any worse than it is at the moment when it comes to the cost of repair. Is there anything else you think is likely to go wrong?

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Just like everyone else I can only guess what might happen - I'm thinking nasty gouges in the side of the cylinder walls that mean machining and expense. (If the engine is to be reused)

If the sides of the cylinder walls are still good and only need a quick hone a proper repair could be made now for less money. But in order to do that the OP needs to have some decent measuring equipment - I don't have a bore micrometer (but I could borrow one) - but it sounds like perhaps the OP doesn't have either a depth gauge or a DTI.

There's a limit / spec in the FSM for replacing just one piston.

Whether it is "worth" investigating further is of course a personal choice thing - whether the rest of the engine is in good enough shape for just one part to be replaced is also a matter of opinion (but hopefully based on more objective measurements)...

...however if the measurements aren't going to happen then this thread kind of goes towards the tyre kicker sucking air through gritted teeth saying "it'll be alright".

It might be alright.

It might not.

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

At this point it's mostly going to be an experiment. The head gasket was only $50 (Victor Reinz), so I'm not out much if it doesn't work. Thanks again for all the info. I'll post more as to how it goes.

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'83 300D turbo diesel (334k daily commuter)
SOLD '80 240D 4 speed manual, #2 piston pitted from crushing a 10mm nut. Running it 'till it burns through.
'78 F-150 300cid 4spd od (with my great unkle's original sales receipt)
SOLD '66 Ford P-350 delivery truck (almost driveable)
'49 Dodge B1D (1 ton Pilothouse era truck) not running but all there, candidate for om617 and 4x4 conversion when money permits.

Don't know if you have read this, but it seems to have some good advice.

http://tinyurl.com/jea5bwx

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

Graham- I hadn't read that, but it seems to confirm what I have been able to piece together from reading on the forum. Thank you. Very good info.

So... I have the engine back together and it starts and runs without the nasty knock. Now on to putting the axles back in place (from towing it home after purchase) and a test drive.

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'83 300D turbo diesel (334k daily commuter)
SOLD '80 240D 4 speed manual, #2 piston pitted from crushing a 10mm nut. Running it 'till it burns through.
'78 F-150 300cid 4spd od (with my great unkle's original sales receipt)
SOLD '66 Ford P-350 delivery truck (almost driveable)
'49 Dodge B1D (1 ton Pilothouse era truck) not running but all there, candidate for om617 and 4x4 conversion when money permits.

Test drive a success! Runs smooth and slow. With a little patience I was able to get it up to 85 though. Transmission seems very smooth. All that's left is to put the hood back on. Current mileage is 263664

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'83 300D turbo diesel (334k daily commuter)
SOLD '80 240D 4 speed manual, #2 piston pitted from crushing a 10mm nut. Running it 'till it burns through.
'78 F-150 300cid 4spd od (with my great unkle's original sales receipt)
SOLD '66 Ford P-350 delivery truck (almost driveable)
'49 Dodge B1D (1 ton Pilothouse era truck) not running but all there, candidate for om617 and 4x4 conversion when money permits.

Yaaay! I always like a story with a happy ending!

As under-stressed as the 616 is, you can likely get years more service out of it with just following recommended maintenance intervals and procedures. Oh and by not beating the crud out of an already compromised engine; that too should be mentioned.

Congrats on your new addition and following your hunch that the engine could be saved.

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2007 Dodge Ram 3500 Cummins Turbo Diesel 4x4
1994 GMC S-15 pickup 4.3 5MT
1985 300 SD
1978 300 CD
1962 220-S Fintail - awaiting restoration

Great! Congratulations!

Love it when we can fix stuff without spending a fortune!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I'd drive it around too and see how long it lasts. Can't hurt. Worst comes to worst part it out and have a bunch of good parts for your other w123.

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Only diesels in this driveway.
2005 E320 CDI 243k Black/Black
2008 Chevy 3500HD Duramax 340k
2004 Chevy 2500HD Duramax 220k

So far, I've put 6000 miles on it. I can't say that I haven't had any problems, but none with the engine yet. (Knock on wood)

__________________
'83 300D turbo diesel (334k daily commuter)
SOLD '80 240D 4 speed manual, #2 piston pitted from crushing a 10mm nut. Running it 'till it burns through.
'78 F-150 300cid 4spd od (with my great unkle's original sales receipt)
SOLD '66 Ford P-350 delivery truck (almost driveable)
'49 Dodge B1D (1 ton Pilothouse era truck) not running but all there, candidate for om617 and 4x4 conversion when money permits.