This is a tester you can build yourself. It's much cheaper than
the so-called "professional" from Hazet or Zeca.
I paid the equivalent of approx USD 50,- for the parts.
You see the coolant reservoir cap which is the only special part. Bought
it from Hazet part nr. 4800-3.
You get the rest from your local compressed air specialist.
The gauge should be connected to your compressor. If you don't have one you use the adaptor which can be driven by a manual pump or the Porsche air compressor. The adaptor is the thing at the lower border of the pictures. Have a tire valve with you when you buy the parts to get the right size where it fits in.
Tips for use:
The standard 924S,944 cap opens at 1.5 bar pressure. My radiator rebuilder
tests his units with only 1 bar pressure. I tested my cooling system even
with 1,8 bar.
Make sure you open the yellow lever slowly and carefully when you
have pressure behind that exceeds 1,5 bar!!! It's better to reduce the
output pressure in a compressed-air system as low as
possible. IF YOU DON'T CARE YOU BLOW A HOLE IN YOUR COOLING SYSTEM!!!
With a manual pump you are not exposed to that risk.
Don't rip the tester away from your coolant reservoir when the system
is under pressure. Release the little wheel to reduce the pressure to normal
level before removing the tester from the reservoir.