x2, induction hardening usually leaves a very subtle bluing on the crankshaft, while this coloring seems far more pronounced. Also the fact that the rod caps show the same bluing. I've never heard of induction hardening of rod caps. Crank yes, rod caps no.

IMO this engine was run without oil, which caused this heat discoloration.

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I'd check out Google images using the search term "OM603 crankshaft". You'll turn up tons of images of cranks that look exactly like the one shown.

This and the fact that there aren't any other symptoms of bearing failure seems to suggest that the coloration came from a manufacturing process.

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I am unsure but have to almost conclude. The responses so far at least. Are partially based on how well your pictures are displaying on members monitors. The reproduction I get is pretty clear that real heat was involved on the rod caps. Also on my monitor the main bearing caps look normal.

The computer I am using is average in my mind. As is the monitor. I have questions about me as an observer but that would be subject to another thread. Perhaps different service providers. Have different qualities of transmission. Individuals color perception also may enter into the picture as well. I use the American spelling of colour to not confuse Americans.

I am interested in what the crank journals are like. I do know that I would be checking the connecting rods for concentric big ends. At least that is a relatively inexpensive issue if it needs addressing.

I would also plasti gauge the rod bearings now. I assume the plasti gauge product is the same. Yet perhaps sold under another name in England. Whatever bearing clearance is present and what the surface of those bearings and journals look like. Can tell a lot in my opinion.

If for example the rods bearings where replaced everything might still be excellent. If the bearing clearances are normal and all appear well. visually. I would not replace them. Checking the main bearings in a similar manner of course.

I am a Canadian and I suspect some of my ancestors where so cheap. They probably swam across from the old country. It is thought by my parents that I am a decendent of sir Francis Drake as well. I never bothered verifying it.

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. :-)

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?.

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 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]