I've got the engine completely apart.
 

Here's a quick follow up to my $500 '80 300SD which wouldn't start. The engine showed low compression, (under 50 psi in 2 holes), so I decided to pull the engine and go through it. I pulled the engine and tranny, and got the engine dis-assembled down to the bare block. 2 pistons were totally junked, lots of worn aluminum and scoring. The crank looks great, as did the bearings. I'll be dropping the block off at the machine shop ASAP, and let them tell me if the bores will clean up with either a 0.25 mm or 0.5 mm overbore. I hope they will, as I can save at least a little dough.

This was my first MB Diesel project, and one thing I have to say - these engines are complex. Lots of fasteners, brackets, accessories, etc. I'm used to working on Chevys and Dodges. I can usually look at any bolt from a SB Chevy and tell exactly where it came from. Not so with the Benz - but it definiely seems well engineered.

Just thought I'd share.

SteveM.

Do you have the factory shop manual for your engine ?
These engines go by very different rules than what you have been used to dealing with...

Cylinder sleeves
 

Granted I have never rebuilt a MB engine, but I thought that the cylinders were sleeved. Am I wrong to think this? If it is sleeved, you should be able to re-sleeve and save some expense.

Maybe you wore through the sleeving and you need to clean up the cylinder walls and then re-sleeve.

Just curious.

Have you priced out pistons $$$$$$$$$$ yet? Make sure you are sitting down when you do.

Yeah, I'm doing the same thing. The best price I've found so far for a set of pistons for my 300SDL is $1217.

Yes, the pistons are EXPENSIVE, but I don't think they'll be as expensive as the SDL mentioned by mplafleur.

I have done this before to a 617. Bored to oversize and used new pistons. It worked out great. Some feel that it is better to sleeve back to standard and reuse the pistons. I prefer not to do this because the pistons in a diesel are HIGHLY stressed.

In your case, you saw aluminum, so you probably have at least two pistons that are not reusable anyway.

Good luck,