I still say its been run with no oil in the past .Then been fully rebuilt .This is how they look . Serched again looking st 20 bottom end strip downs and i see nothing with those discolouring marks on Good luck with the rebuild if it worked before tou have nothing to worry about .

This is one i found .They all looked the same no sign of overheating.Your picture of engine no 1

Attached Thumbnails

     

Thanks to everyone for the comments, and in particular thanks to 97 SL320 for leading me down the path to enlightenment.


It seems the crank journals and con rod caps were subjected to an Induction Hardening process. This particular OM 603 is from a British Army BV 206 which has been through the Army Base Repair system, so I'm not sure if the process was done then or whether all OM 603's are like this straight from Mercedes.


As for the rod movement, 97 SL320 is correct, these engines have piston guided rods.
Interesting stuff, I enjoyed reading up on the subject. :-)

Your welcome.

Given you have access to mil spec stuff, I'll take a Ferret. I so wanted to show up at the front gate of one old work place and poke my badge out of the turret using a stick. I think the guards would run away.

Some crankshafts are totally black ( except for ground journals ) from chemical hardening. The induction hardening is done after rough machining as the heating will warp the crankshaft, the crank is then straightened and final ground.

Random comment: When they re-grind a Crankshaft a stream of coolant/lube is used so re-grinding a crank would not cause the discoloration.

__________________
84 300D, 82 Volvo 244Gl Diesel

Well you must have a better google images than i do .Checked this out 2 days ago i see nothing like posters crank. If you can find one like it i will shake your hand .Can you post one up so i can see please?.

" I use the American spelling of colour to not confuse Americans."

Too late .

I'm concerned as the partial view of the rod bearing journal in pic. #1 looks suspect to me .

? Do you have any pictures of the crank journals ? . that would clear things up pretty quickly .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Go use that exact search term. You'll find several without even scrolling down the page. The images you posted above are NOT an OM603 crankshaft. The 603 is a 6 cylinder, you posted a 4.

Here's an excellent example, notice that the bearing journals are in good shape and how uniform the "bluing" is, this one also has it on the main bearing journals:

__________________
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!)

These journals look fine, not so the single one in pic. #1 .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

This thread isn't a discussion over journal wear, it's whether or not the "bluing" is normal on the 603. The photo in my post above is an example of a good-condition crank showing the exact same bluing as the OP's crank, suggesting the "bluing" is a result of a manufacturing process, not overheating.

__________________
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!)

Yes but ;

Anyone who mindlessly assembles an engine with a rough looking journal like in Pic. #1 where it looks to have been oil starved, can expect short engine life .

This is a good thread, I too noticed the main bearing caps don't have the same coloring as do the rod caps .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

The crank is out now. I'll try and get some decent photo's tomorrow.

Sounds good .

I like Bench Works, I find it very satisfying even after all these decades .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

I posted up several pics last night (U.K. time). I got a message saying "your post will not be visible until it has been cleared by a moderator".

As it still isn't up I presume there must have been a problem with it.

Here goes with one pic.

Well that seems to work. Are you not allowed to put several pics in a post ?