Date:         Sun, 17 Jan 1999 09:08:02 -0800
Reply-To:     Vanman <mckayaa@OIT.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Vanman <mckayaa@OIT.EDU>
Subject:      Re: A "metallurgical" 2L engine rebuild Q
Content-Type: text/plain; charset="iso-8859-1"

-----Original Message-----
From: Tom Young <young@SHERLOCK.SIMS.BERKELEY.EDU>
To: vanagon@GERRY.VANAGON.COM <vanagon@GERRY.VANAGON.COM>
Date: Saturday, January 16, 1999 5:17 PM
Subject: A "metallurgical" 2L engine rebuild Q


>Hey everyone:
>
>I cleaned up the 6 large case "through bolts" on one of the Vanagon
>engines I'm rebuilding and I noticed that a couple of them are really
>beautiful - a gorgeous shade of violent, like they'd been anodized.  Is
>this color really the result of tempering of the steel (too hot) and do I
>need to replace these bolts?
>
>TIA.
>
>---------------------------------------------------------------------
>Tom Young               young@sherlock.SIMS.Berkeley.EDU
>Lafayette, CA  94549    '81 Vanagon
>---------------------------------------------------------------------
>
What caused this engine to fail?  What I would do is to take a look at a set
of brand new bolts and compare their colors (look for shades of blue and
rainbow colors).  My experience with all of the diesels I've worked on, is
that you only get those colors when the metal gets WAY too hot, and that if
we found anything that changed color like that, we would : (1) replace the
part as it had been hardened and would be liable to break (esp. a bolt; if
it gets harder, then it gets brittle and it will not stretch like it should
when you torque it, instead it may break off before or after the job is
done); (2) figure out what would get the bolt so hot as to make it change
color.  I would check the block for damage VERY closely (esp. for cracks and
tolerances), as the block would have to get very hot also.  Of course, this
is also a VW aluminum block, instead of a Cummins cast iron block, so every
thing I just said, if proven not true, can be explained by this, but I think
metallurgy is the same from engine to engine.  Hope this helps...

-Aaron Mckay
                                 mckayaa@oit.edu
                                 college student in mechanical
                                 engineering at Oregon Institute of
Technology
                                 '85 vanagon GL