Adam's Canadian 13B Rotary 818-SR Build

[Toysrus]

Or wrong cap, plunger not sealing the hole. Putting the pressure tester in it's place would temporarily solve it then you can watch to see if the coolant gets forced out of the overflow tank. Or if you don't have a test cap you could rig up a plug to seal the radiator cap hole and force the 16 psi cap to do it's job. Don't really need a normal cap there anyway a cap that doesn't release pressure would work. https://www.google.com/imgres?imgurl...act=mrc&uact=8 like the one on the right just make sure whatever you used to plug the overflow port can take the pressure.