A little advice on using a cooling system pressure tester. Start the engine and then hook up the pressure tester. While the engine is running check for leaks. Dis-connect the pressure tester and then shut off the engine. From experience if you do not have any idea where the leak is and it happens to be an internal leak that is into a cylinder, AKA head gasket that is leaking into cylinder and or intake gasket, you can hydraulic the engine if you leave the tester connected with pressure applied and you shut off the engine for even a short period of time. If the coolant leaked into a cylinder and you re-start the engine more than likely you will break the starter and kiss a rod good by. If it is an almost know leak such as an intake gasket that leaks externally and you just want to verify, then using the pressure tester will probably make the leak that much worst and or make it so you need to fix it right then. Just some info. Later.