S65 Blue color on Crankshaft. Need help.

[guram1993]

2008 E92 M3 DCT 85k

Going with BE bearing and ARP Bolts.

I got a call from the shop they noticed Blue Coloring on CrankShaft.

Possible main bearing issue they said.
I dont completely agree, because there is no evidence blue coloring started from near/around bearings/journals. Because heat mark (blue Marks) are not coming from the middle, rather they just show up at the ends of counter balancers.


I'd like to know if anyone knows why its blue ? Possible from hardening process at manufacturing ? if so why isn't the complete crank same color rather than only near rear end of the engine ?
And what could have cause it to turn blue ? bearings do not look toasted at all, they have same wear everyone has experienced, maybe little more chip than even wear.

Here are some photos .

https://drive.google.com/folderview?...mtyuePp-vC8dTQ

I went for a visit I took videos and pictures. They had 2 sets of bearings off already .

If anyone has time to look through these and let me know what they think, that would greatly be appreciated.

Thanks in advance.

[Helmsman]

Woah...that was one strange colour. Will be really interesting to see what Deansbimmer and the other wngine folks can say about this.
Couldn't open your google file, what did the rod shells look like?

[///M Power-Belgium]

My theory is that your crank went through a faulty hardening process => Overheated
Your link shows an error 400 .

[Pig Farmer]

This may be helpful...

https://www.m5board.com/vbulletin/e3...haft-blue.html

[Helmsman]

Bump, curious on some experts comment on this.

Cheers

[pbonsalb]

Mine were totally clean. There were 4 different shafts used in these motors (same journals) so my 08 may not compare to the op’s crank.

[Helmsman]

Originally Posted by pbonsalb

Mine were totally clean. There were 4 different shafts used in these motors (same journals) so my 08 may not compare to the op’s crank.

Same here, mine was clean as a whistle (2011.5)

[deansbimmer]

It's from the factory. They're hardened in lots in a wire cage. That crank was just closest to the mesh. Nothing defective, carry on.

[guram1993]

Thanks Everyone for giving your opinion. I do think this is something that happened during the hardening process. I can not find heat source if this did happen while driving lets say.

Here is another try at the google link for more photos.. I will post the rod bearing photos as well to show their wear. I had few that had copper part exposed, mostly its normal wear i have seen on on the threadbare when people pull them as preventive maintenance rather than after failure.

Please let me know if this link works..

https://drive.google.com/open?id=1lm...mtyuePp-vC8dTQ

[guram1993]

I also received this link from my fellow e46 fanatics. It shows that complete crank is blue. much darker blue.

http://www.m3forum.net/m3forum/showthread.php?t=379165


And also the crank shaft you see exposed with rod bearing removed. That's the Same one that's blue in previous photos. In that picture balancer is positioned on top.
Here is the bearings that came out.

[Helmsman]

Originally Posted by deansbimmer

It's from the factory. They're hardened in lots in a wire cage. That crank was just closest to the mesh. Nothing defective, carry on.

Nice conclusion and for OP to know. I'd be worried as well.

[deansbimmer]

Originally Posted by guram1993

I also received this link from my fellow e46 fanatics. It shows that complete crank is blue. much darker blue.

http://www.m3forum.net/m3forum/showthread.php?t=379165

The S54 cranks are hardened through a different process than the S65. All those cranks are blue.