Hmmm... no. But that could work- with the system cold and no pressure,
just "grind" it into the pinhole with a thumb.

If practical, for a pinhole leak take a piece of wire that is longer than
from
the hole to the nearest radiator opening.  (Obviously out of the vehicle.)

Strip the insulation off the wire and throw the wire away.

With a SMALL drill, enlarge the pinhole.  Then feed the insulation through
the
enlarged pinhole and out opening.  Now put a 'tack' into the insulation
tube.
Smear a bunch of goo you want to use to seal with on the underside of the
tack and carefully PULL the tack into the radiator till the spike sticks out
the hole.  (The hole you drilled MUST be large enough for the tack with
the insulation over the spike to fit the hole!)  Let it set/cure.

When it's almost set, but not 'hard set' clip off the external spike.

The advantage of this is you now have a 'compression' fix against radiator
pressure, not a patch that can be 'blown off' by radiator pressure.

Although I'm leery of putting a 'tack' in my radiator...

If possible, I'm much more comfortable with enlarging the hole to where
I can use the same trick to feed a small 'bolt' with a big washer on it,
even
rubber washers if possible, from the inside of the radiator and once it's in
place then put a washer and nut on the outside with even more goo to
'pinch' the radiator tank body.  Then when I'm satisfied, I much up the
exposed threads of the bolt so there's no way the nut could come loose.

I understand where you're coming from on that, but I've got to question
the ultimate wisdom of that practice.  I guess the idea is to put a
ceiling on the max. system pressure for moderate temporary pressure
spikes.  My concern would be a situation of moderate to serious
overheating in which the 15 psi cap may (not guaranteed, but may) at
least prevent flash boiling and reduce the chance of engine damage,
whereas in the same situation, the 7 pound cap will possibly totally let
loose in a flash boiling suddenly leaving critical overheated parts that
are accepting even more heat from even hotter other parts unsurrounded
by liquid coolant.

I guess there are different but real increases in risks either way, but
I would think the right way is to do preventive maintenance (use the
right coolant, change it before it on a realistic scehdule) and replace
any and all weak parts (certainly old hoses, any radiator showing signs
of age, etc.).

The 7 psi cap seems like a bandaid to me.  The primary goal is to
protect the engine - not to protect weak parts in the coolant system
that need to be replaced.  Again - the 15 psi cap may prevent flash
boiling (and engine damage) in a situation in which the 7 psi cap would not.

IMO...

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

I don't think there's ANY way that a Chrysler LH will run with less than
12-14 psi of cooling system pressure. These cars, like most modern cars,
operate at significantly higher temperatures than older cars for better
fuel efficiency, lower emissions, and (although it isn't intuitive) less
wear. You can run a '49 Plymouth with NO radiator cap and at most a
small waft of steam will come out the radiator neck. If you just *idle*
an LH car to get it up to operating temperature without a cap, coolant
will boil in the cylinder heads and send a geyser out the neck. Heck,
even my '66 Dodge *needs* a 12-14 psi cap to avoid pushing too much
coolant into the overflow tank, and that's just with a 180-degree
thermostat, not the 195 or 210 thermostats like modern engines use. Even
if you can run the car at lower pressure, you can be sure that you are
having "microboiling" going on in the heads creating steam pockets that
result in hot-spots, and cavitation that erodes metal from the inside of
the cooling passages. Lowering cooling system pressure is ONLY a
reasonable option if you do something like convert to one of the
waterless coolants like Evans NPG. And then you give up some heat
transfer capacity in the process.

a lower rating pressure cap will result in higher engine temp
the pressure spec  is directly related to heat dissipation thru the raditor
get a new raditor and quit screwwing around a engine rebuild is too much money
on a 2.7