Make an Auto Radiator Pressure Tester

Step 3: Tire pressure gauge

I selected and bought a dial indicator tire pressure gauge identical to this one. Its outside diameter at the end fits nicely inside a piece of 5/16 inch I.D. fuel line hose.  This gauge holds pressure until the brass release button on the side is pressed.  You will want to watch the gauge to see how fast it leaks down when the tester is in use.  I removed a valve core from the end of the gauge before attaching it.  Another option is to use a gauge that does not have a pressure release button.  (The photo is from Google images.)