I have a photo of just such a thing I made up... couldn't be much easier..
can even use the cap you have and a old valve stem (all over the floor of
some messy shops) and a short length of tube... I used it to bleed my rad
once... you pump in some air......open your bleeder on the rad and let out
air until you tank level gets down to the side hose...close bleeder valve...
take off the cap.... add more fluid,..... repeat until all air is out of
system...
anyone interested send me a p-mail I'll bounce the 70k .jpg back.
RR

Orginal message
>>Date:    Fri, 3 Jun 2005 10:50:49 -0400
From:    Mark Cumnock <kayakwesty@YAHOO.COM>
Subject: looking for a tool to pressure test my coolant system

>>has anyone been there done that?

I assume that you take off the burp tank cap and install the pressure
tester there.

Has someone found a tool that works go for this and installs on the Burp
Tank?

Can it be found at a flaps?

Mark