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<I've done a air amount of gas tank soldering (hard to avoid on MG
T-Types with their soldered tank seams) and have yet to blow myself up.
Flooding the tank with inert gas is the preferred method, but beyond the
scope of the average home workshop. Here's what I do:
o Drain tank completely.
o Remove tank from car.
o Leave tank out in sun with all caps, plugs, and other fittings
removed to let the remaining gasoline evaporate out. If you > can arrange to
blow air through it at the same time, this will speed things up.
o Wash out the tank thouroughly with a detergent solution. Then rinse well.
o Solder.>
Gas tank repairs and open heart surgery should only be done by professionals.
IMHO I think you have been lucky that you haven't blown yourself up. What
you describe will work most of the time but it's still russian roulette!
Lacquer deposits typically found in tanks are difficult to remove as you
described and can disociate with the application of heat, generating
flammable fumes. It really isn't worth the risk. An inert gas (such as
Argon or Argon/CO2 from a MIG welder) purge will do the trick. You should
run a purge until you have a minimum of seven volume changes through the tank
(more is safer) and maintain the purge the whole time you are working. If
you don't have access to inert gas the next best thing is to clean as you
described and fill the tank with water. Position the area to be worked so it
is the highest point, just above the water line. This will reduce the volume
of potentially explosive fumes.
There are people who repair tanks for a living and it is not particularly
expensive. A shop that services tractor trailors is usually equiped to do
the work or can refer you to someone who does. Just about any place that
sells automotive parts will sell you a 2 part (catalyst) gas tank putty that
works great on small holes.
This post is in memory of young Mr. Modar who welded lots of unpurged tanks
of which only one repair was unsuccessful.
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