[Vwdiesel] Initial Diagnosis: 1998 VW TDI Jetta

[James Hansen]

Actually, you do use observation to diagnose bearing wear, stuff a mic
simply cannot tell you.  The wear pattern definitely diagnoses certain
things, what the oil was like, if the rod is bent, if the installation is
correct, bearing crush, all sorts of stuff.  Mic internal bore, and crank
external journal, and you only know size, not orientation- if it is still
square, or if it needs to be align bored (honed) or what have you.  Not to
dis the measuring tools, but diagnostic disassembly is a lot of touchy feely
stuff, some tolerance checking (I have seen perfect looking cranks that were
worn undersize) but a lot of how it looks kind of technical diagnosis.
Check this out, specifically things that are really really hard to measure
for a home shop guy- like journal alignment, bent rods, etc.
http://catalog.mahleclevite.com/bearing/
Shoot, I bet there is maybe one mechanic at best in any shop in town that
even knows how to check this stuff, let alone measure it or correct it.

I tell ya, I have years of engine disassembly behind me, and you can learn
more from ten minutes with this link, than I did in years of pulling apart
dead stuff. It's pretty cool to have this resource available online.  I have
learned- plastigauge is a guideline, nothing more. The mensuration tools are
only as good as the experience of the observer reading them. (use a dial
bore indicator and get back to me if you don't agree) That said, you can't
spend enough on good measuring tools if you really want to get it right/
technically perfect/race the bag off it.  The more I learn, I learn I know a
lot less than I thought I knew before I learned I needed to know more, (and
usually it involves spectacularly broken expensive parts).  I should put
that on my cabinet that has all the race engine stuff in it, it's easy to
forget.
-james



-----Original Message-----
From: vwdiesel-bounces at vwfans.com [mailto:vwdiesel-bounces at vwfans.com] On
Behalf Of brian hoeft
Sent: January-09-11 4:07 PM
To: Erik Lane
Cc: vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] Initial Diagnosis: 1998 VW TDI Jetta

I'm not trying to be wordy or combative here, but I see more observation and
speculation than actual diagnosis, as the title reads.

Stephen, what evidence do you have other than observation to make your
determination on the bearings and other internals? I agree that they are
very good for upwards of 300k miles, but a plastigage/micrometer session is
much more accurate than casual observation, even if you had a trained eye.

I don't see ANY measurement of anything for that matter.