Snap-on pressure gauge and hand pump connected in an engine bay…

Cooling System Pressure Test

After filling the system absolutely full (no air), and checking every connection for proper closure & clamp tightness, install a pressure tester and apply as much pressure as the cap is designed to hold. It may be necessary to leave it overnight before enough liquid escapes to find the leak. Or it may be necessary to pump it up several times, if the liquid is collecting in a hidden pocket on the engine or frame. It may even be necessary to use a stethoscope (probe removed) to listen for the hissing or gurgling.

Don't forget to check the heater core, and its drain from the firewall.

Owner caption September 2014 · Photo 5239 of 6546