I too, like the underwater epoxies out there on the market, but don't
kid yourself about the marine epoxy actually bonding to the
polyethylene plastic that the tank is made of.  I think the reason
your patch is "sticking" to the tank(as opposed to "bonding") is
perhaps the epoxy was forced in the convolutions of the hole well
enough that the wad of epoxy pushed through in some sort of
hourglass(can't think of a better way to describe it)  fashion where
it is filling the hole and surviving the 14psi in the system for
now.  I'm glad to hear the marine epoxy is surviving the 200+ degree
F temps.  If the hole were small enough, I'd have been more tempted
to ream out the hole with a small drill bit and run a stainless steel
sheet metal screw in the hole and seal it with a rubber washer or
silicone(might not even need the washer).  Prolly didn't have the
drill and such to do that fix on the side of the road though.

The only adhesive I've ever gotten to bond with polyethylene is a
urethane based 2 part adhesive sold by the Old Town Canoe company for
bonding kevlar felt grunch pads to the bottom of their cross linked
polyethylene canoes.  It involves polarizing the plastic by exposing
the plastic briefly to the blue flame of a propane torch before
laminating the material.  Good surface prep is also required.  the
shelf life of this urethane adhesive is like 6 months, so storing in
the tool box is not a great idea.  I guess we've all been there.

DM&FS

At 01:01 PM 10/10/2006, John Meeks wrote:

>Hi Folks ~
>Here's a handy item to have aboard.  "Marine Epoxy Stick" from bondo.
>After work Friday, I was stopped at a light when I noticed steam billowing
>out of my side vents and back of the van.  "Oh Crap" thought I. Major
>trouble here. When I pulled over and popped the hatch, there was a small
>stream of coolant squirting out the expansion tank just below the cap into
>hot exhaust parts. Looking through my small box of repair items I found "the
>stick", an item that had caught my eye in the  Wal-Fart auto section a few
>months before.
>
>After letting the engine cool, I filed off the crud around the hole  and
>cleaned out the crack. I cut off about an inch from the stick which is kinda
>like a white tootsie roll in consistancy. Kneeded the piece till it was nice
>and uniform feeling and jammed the stuff into the crack, spreading it out to
>feathered edges into about a 1 by 2 inch oval shape. Just like putty. Let
>dry for an hour and it's rocklike.
>
>I've had no leaks while I wait for a replacement tank and I've driven over
>many miles of milled pavement which really vibrates everything. This stuff
>would work for many of the plastic parts in our systems and I can say it's
>worth having along...
>
>Safe Travels,
>John Meeks
>
>Vanagon Rescue Squad
>http://www.vanagonauts.com/Vanagon_Rescue_Squad74.htm
>
>'91 Westy MV
>'85 GL  "Byron"
>Top o' Northern Michigan
>KC8ZFN
>
>
>
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