Sam Nickaby wrote:
I am trying to glue my plastic radiator tank using Elmer's
Polyurethane Glue just to see if it'll hold. I've heard that this
worked fine on small pinhole leaks by a few people. The
problem is that when ever the glue dries bubbles or foams
are formed on the glue in about 2 hours.

Is this the Pro Bond stuff?

This bubbling is a feature of some polyurethane adhesives, which are
designed to expand to fill gaps. I believe that it's a reaction with
water. The piece doesn't have to be wet because there is water in the
atmosphere. E.g. moisture-cured polyurethane coatings get their
moisture from the air.

Get a two-component epoxy instead. Perhaps one of those that come
pre-formulated with fillers that turn them into a putty.

There is that one product whose epoxy and hardener are both filled to
form a paste and also dyed different colors (black and white). You keep
mixing the two until the resulting paste is evenly gray.

The foam is a bad
thing because it's very brittle. What is the proper way to use
this glue so it won't foam?

There probably isnt'.

By the way, don't use this ****, it contains isocyanates, which are
very hazardous to your health. Check out the MSDS:

http://www.hunt-corp.com/msds/mp9401.htm

8.3 Exposure Guidelines

Diphenylmethane 4,4'-Diisocyanate 101-68-8
ACGIH TLV: 0.005 ppm (0.051 mg/m³) TWA

Note that 0.005 parts per million is a ridiculously small threshold
limit value. Contrast that with the solvents typically used in lacquer
thinner, whose TLV's are typically on the order of 100 parts per
million! Xylene: 100 ppm; Toluene 50 ppm; Acetone 750 ppm. What else?
Oh yes, Butyl-Acetate for slower drying: 150 ppm.

You don't want to get sensitized to isocyanates, because polyurethane
foam is everywhere. Seat cushions, insulation, moldings in car
interiors, etc.