From: John De Armond
Newsgroups: rec.outdoors.rv-travel
Subject: Re: radiator fix
Date: Wed, 24 Jan 2001 23:32:09 -0500

sportscoach@my-deja.com wrote:
>
> Hi all
>
> I've got a small leak in my radiator at the filler neck area,I'm away
> from home and would like to put a temp patch till it get home then have
> it silver soldered properly..does anyone have a suggestion on a product
> that will handle the heat that I might find in a auto parts store? Thx

Yup, been there, done that.  The problem is, the radiator tank that
the filler attaches to is thin and flexible and expands and
contracts significantly as the temperature and pressure varies.
There is nothing that will adhere under these conditions enough to
seal for long.  But there is a way.

What you must do is pull epoxy or silicone through the leaking joint
so that it flares out inside the tank.  When it cures, there is a
mechanical lock between the sealer and the tank.

The technique is simple.  use a high strength epoxy (JB weld or
equiv).  The epoxy must be heated to thin it so it will freely
flow.  I do that by heating the radiator area with a heat gun or
hair dryer.  Once the epoxy is thin, it must be forced through the
defect.  The easiest way is to pull a low vacuum on the cooling
system.  This is easily done using one of those plastic hand-held
vacuum pumps sold at car parts places for checking vacuum advance,
purging brake systems and such.  The trick is determining when some
epoxy has been pulled through.  If you lay it on thin over the
defect, the area over the defect will sorta pucker in as the epoxy
is pulled in.  If the defect is near the filler cap like yours, you
can simply feel in there with a finger.

This is somewhat of a balancing act, because heating the epoxy
enough to get it to flow greatly speeds up the cure rate.  Epoxy
that normally takes 24 hours to cure will harden in minutes so one
has to be ready.

One of the hardest things is to force yourself to open up small
defects so that the epoxy can flow.  Ya gotta make a small leak into
a larger one.  Not bad once you do it once :-)  Wiggling a knife
blade down in the defect will usually do the job.

This works amazingly well.  I drove my 68 Fury for over 5 years with
a tank seam sealed using this method. I've done this same fix for a
number of friends and family and have yet to have one fail if the
underlying metal was sound. One thing to keep in mind before you do
anything to the radiator.  Once you put goop on it, it may become
impossible to properly repair it because the goop will prevent
solder from sticking to the brass.  The chemical cleaning that the
radiator shop uses will not remove epoxy.  Be prepared to buy a new
radiator.

John