Date:         Thu, 3 Jan 2002 20:49:51 -0800
Reply-To:     Mark Keller <kelphoto@ISLANDNET.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Mark Keller <kelphoto@ISLANDNET.COM>
Subject:      warm up and coolant pressure on head gasket seals
Content-Type: text/plain; charset=us-ascii

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