Date: Fri, 4 Jan 2002 08:15:58 -0800
Reply-To: gary hradek <hradek@YAHOO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: gary hradek <hradek@YAHOO.COM>
Subject: warm up and coolant pressure on head gasket seals
Content-Type: text/plain; charset=us-ascii
Mark,
I am not sure about your conclusion about clamping
pressure. Seems to me that the head bolts are
shorter when it is cold and the antifreeze water
mixture becomes more dense(temperatures below
freezing). I think the cold leak hypothisis is better
explained by increased local high pressure systems
that develop from the extreme temperature differential
between the hot coolant and the cold engine. This
being the case, perhaps it is better to simply get in
and drive.
regards gary
Date: Thu, 3 Jan 2002 20:49:51 -0800
From: Mark Keller <kelphoto@ISLANDNET.COM>
Subject: warm up and coolant pressure on head gasket
seals
Greetings Listees,
The following article is largely speculation on my
part, but I offer it
as my belief and treatment to the waterboxer's head
corrosion problem.
It is my opinion that it is better to allow the wbx
some time to warm
up.
I allow engine to operate at or below 2000 rpm until
I see the
temperature gauge move. I believe it to be a good cold
weather practice
because of the following scenario I've developed--
largely just
thinking about the head leaks and reading the list. I
do believe the
thick rubber water jacket gasket uniqueness of the
waterboxer is a
better clue
head corrosion better than the fact that engine is
aluminum.
The VW waterboxer differs from other water-cooled
engines in that it's
cylinders are not cast into the block. The result is
that the steel
head studs are extremely long. Steel expands and
contracts at a
different rate that aluminum alloy. Over short
distances no problem,
but the long steel studs and cylinder jackets create a
situation where
a cold engine could have a significant drop in
clamping force over the
water jacket gasket than same engine at warm operation
I feel that's why the waterboxers coolant system
utilizes the thick
rubber gaskets which seals the cooling jackets. These
pliable gaskets
are necessary to compensate for the different
expansion of the water
jackets and the steel head bolts during cold
temperatures. That why
leaks are spotted first on cold engines and go away
when the engine
warms. In the early vanagon versions this seals
hardened prematurely
and later were of a modified compound. VW coolant may
have contained an
additive to maintain pliability.
It's the pliability of these gaskets that keeps
sealing qualities when
the engine is cold and thereby keeps the coolant from
getting beneath
them. So while I do not specifically know, I suspect
that the VW
coolant may have had an additive at one time to keep
these gaskets in a
pliable condition.
Another issue which I feel affects the ability of
these gaskets to
seal
during the cold is clamping force. When the engine is
cold the
clamping
force on the gaskets is less due to the differential
contraction rates
of
the long steel studs and the aluminum alloy water
jackets. As the
engines begins to warm, the clamping force on the
thick water jacket
gaskets increases due to the expansion of aluminum
alloy
Lastly with operation a cold engine at the high rpms
of 3000 could
cause the coolant pressure could to be high enough to
be pushed beneath
the water jacket seals due to low clamping forces and
a closed
thermostat and a water pump impeller capable of
pushing coolant over 30
ft of hose.
Even with the heater loops open , I feel that engine
operation should
stay below 2000 RPM for a couple of minutes, to allow
the cooling
jackets metals to warm up, and keep coolant from
entering beneath the
water jackets.
Sincerely,
Mark Keller
91 Carat
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