[s-cars] Coolant system pressure tester recommendations?

[Kevin Day]

Theodore Chen writes:
> can you make one from a coolant tank cap?  drill a hole in it
> and install a fitting so you can pressurize the system?  i haven't
> looked at it closely so i don't know how it vents.

Yes, you can.  See here:

http://www.boost-instruments.com/coolantpres.jpg

As you can see I used my brake bleeder as the pressure source.

To adapt the cap, I  took the pressure relief valve parts out, drilled
a close fitting hole, screwed in a 1/8 NPT hose barb, and filled the
bottom with RTV.  Then I put the sealing O-ring back in, and screwed
it back on the reservoir while the RTV cured.  I don't have a picture
of the inside of the cap but it was pretty simple.  The need for the
RTV is obvious -- the cap won't seal otherwise due to the grooves cut
for the pressure relief function.

It works well.  Another way to do it which I used before I made the
adapter is to leave a normal cap in place, remove the small hose from
the overflow tank and plug it with something (a 3/8" socket extension
works), then attach the pressure source to the tank nipple where the
small hose normally attaches.

-Kevin
(survivor of many, many Audi coolant leaks)