Does anyone know where i can locate a dummy spark plug tester so i can attach an air line to it to fill the chambers with compressed air. The reason for this is i have a car with a suspect head gasket (loosing water but no leaks). Ive compression tested it but all are fine at 175 each. This test will show an increase in water level or even air bubbles in header tank if the head gasket has gone. Seen them before but cant locate 1 where i am.