When/why we need x-member bracing

[mkii_84@yahoo.com (Andrew Wong)]

Yes its near the radiator.  I suspect paint chipping
also.  My front motor mount is bad so probably the
shaking up front could do something to the paint
--- Neal Tovsen <nealtovsen@yahoo.com> wrote:
> Well, they are definitely stress marks in the
> *paint*,
> but that doesn't mean that the metal is cracking. It
> could be from the metal underneath flexing, but it
> could also be from moisture getting underneath and
> separating the paint from the metal.
> 
> I have those already on my freshly painted raintray,
> but I suspect it might have something to do with the
> sledgehammer I took to it to clear the throttlebody.
> :)
> 
> Is that near the motor mount? Looks like on top of
> the
> radiator support...
> 
> Neal
> 
> 
> --- Andrew Wong <mkii_84@yahoo.com> wrote:
> > Neal would these be considered stress marks on my
> > Scirocco.  Its an 84 Scirocco built in 12/83 so it
> > has
> > the small tank and full size spare.  Even though I
> > am
> > in Florida, that area has some rust frrom being a
> > northern car so I am unsure of what these lines
> are.
> > 
> > My 84 is complety stock also
> >
>
http://camo.flage.net/vag/view_photo.php?full=1&set_albumName=albuo48&id=P3050123
> > --- Neal Tovsen <nealtovsen@yahoo.com> wrote:
> > > > > I have a theory here, so y'all get out your
> > > flame throwers!
> > > > > The theory is based the fact that I've had
> my
> > > Scirocco for 18.5 years and
> > > > > have always driven it hard. Not slamming
> > shifts,
> > > but alot of WOT and high
> > > > > RPM downshifts. In other words, I've had as
> > much
> > > opportunity to crack my
> > > > > chassis as anyone and to date, with 240,000
> > > miles, NO cracks.
> > > 
> > > I pulled this portion of the crossmember thread
> > into
> > > its own new thread. 
> > > See the two relevant emails below if you haven't
> > > been following.
> > > 
> > > I've been doing a lot of thinking about WHEN and
> > WHY
> > > the crossmember
> > > cracks appear, in combination with the people
> who
> > > have actually said
> > > that they've experienced this problem.
> > > 
> > > Is there ANYBODY out there who has an '84 or
> older
> > > Scirocco with a
> > > cracked front crossmember? If there are any, I
> bet
> > > it's only a couple
> > > people out of the bunch. I dawned on me one day
> > that
> > > I haven't heard of
> > > anyone with this problem on a Mk1 or on a
> pre-'85
> > > car. Nearly all of
> > > them have been 16v's, and I think the 8v's were
> > > later cars too.
> > > 
> > > While it is obvious that improper alignment of
> the
> > > motor mounts could be
> > > a contributing factor, there is one important
> > thing
> > > that happened after
> > > '84. In 1985, VW changed the floor pan of the
> car
> > to
> > > incorporate the
> > > space-saver spare tire and larger gas tank. At
> the
> > > same time, the design
> > > of the car changed a little bit across the whole
> > > car. Most importantly,
> > > the type of steel used was changed! It was
> > supposed
> > > to be (and is, from
> > > my experience) much more rust-resistant. This
> > became
> > > clear when I was
> > > welding the floor pan from an '85 into my '77,
> and
> > > was reinforced by an
> > > autocrosser who isn't on this list who has also
> > > studied the floor pans
> > > of the different year Sciroccos. 
> > > 
> > > The '85 floor pan I had was very obviously of
> > > different material, and I
> > > am starting to believe that it is more prone to
> > > stress cracks.
> > > 
> > > The only other possibility that fits this theory
> > > somewhat is that in '86
> > > we started seeing higher-output 16v engines.
> > > However, that doesn't
> > > explain all the souped-up 8v's and 16v
> transplants
> > > into earlier cars
> > > that seem to all do fine.
> > > 
> > > So let's test the theory. Anybody out there with
> > an
> > > '84 or older
> > > Scirocco with crossmember cracks? Dan Bubb, what
> > > year is your car?
> > > 
> > > Neal
> > > 
> > > On Tue, 2003-03-04 at 17:48, T. Reed wrote:
> > > > Dan,
> > > > 
> > > > That's a very interesting theory, and I did
> not
> > > know that the front mount
> > > > was an add-on!
> > > > 
> > > > I think you're probably right to some degree.
> > But
> > > take note that just
> > > > about every case of cracked crossmember I've
> > seen
> > > (and maybe people will
> > > > jump out here to prove me wrong - feel free!)
> > has
> > > been on a Mk2, usually
> > > > with a 2L 16v. And the cracks typically
> develop
> > > within a year or two of
> > > > upgrading the engine. Those has just been my
> > > observations, though. I'm
> > > > sure I'm gonna catch flak for saying that..
> > > > 
> > > > Personally, I think poly mounts are a big
> > > contributor. I have a poly front
> > > > mount and a vw motorsports rear mount and when
> I
> > > jump on and off of the
> > > > gas very quickly the whole car jerks around
> like
> > a
> > > friggin air hammer.
> > > > That kind of pounding has got to do bad things
> > to
> > > the thin sheetmetal
> > > > that vw spot welded together to form a
> > > crossmember.
> > > > 
> > > > -Toby
> > > > 
> > > > On Tue, 4 Mar 2003, Dan Bubb wrote:
> > > > 
> > > > > I have a theory here, so y'all get out your
> > > flame throwers!
> > > > > The theory is based the fact that I've had
> my
> > > Scirocco for 18.5 years and
> > > > > have always driven it hard. Not slamming
> > shifts,
> > > but alot of WOT and high
> > > > > RPM downshifts. In other words, I've had as
> > much
> > > opportunity to crack my
> > > > > chassis as anyone and to date, with 240,000
> > > miles, NO cracks.
> > > > > The two powertrain mounts that do the most
> to
> > > dictate the position of the
> > > > > engine are the side mounts. They sag with
> > time.
> > > The rear and front mounts
> > > > > can be adjusted to accomodate this sag to
> some
> > > extent. But, if they're not
> > > > > adjusted they end up supporting most of the
> > > weight when their main function
> > > > > (imho) is to resist powertrain torque. So,
> if
> > > you never adjust your front
> > > > > and rear mounts and don't replace your
> > passenger
> > > side mount regularly, you
> > > > > have an abnormal load on the front and rear
> > > mount. The front is the least
> 
=== message truncated ===


=====
-Andrew Wong 
1984 Black Scirocco
1987 White Quantum wagon

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