For those of you who suspect leaking heads but are desperately clinging to
the vagrant air bubble hope, Eastwood has an inexpensive cooling system test
kit that will detect exhaust gases in the coolant. It is simple and easy to
use. Their price is $44.99 and shipping.

The link: http://www.eastwoodco.com

You are looking for item 46134

Text of their description:

                   COMBUSTION LEAK TEST KIT
                           Item-no 46134

Test for Exhaust Gases In Your Cooling System. Leaking cylinder
head gaskets, cracked/warped blocks/cylinder heads can all lead
to complete engine failure. Verify the problem with this easy to use
kit. Tapered nose on the test chamber fits the radiator neck of
most gasoline, diesel and LPG powered engines. Included Blue test
fluid turns yellow if exhaust gases are present. Includes test unit
with vacuum bulb, one pint of test fluid for approx. two dozen tests,
and complete instructions.

Hope this adds comforting data to someone's situation.

Frank Grunthaner