there is a liquid check that involves drawing up air from the radiator and bubbling it through the checking fluid with a suction bulb. If the liquid turns from blue to yellow, you've got a small combustion gas leak into the coolant. If it turns green, you've got a big leak. Check the NAPA store for a "block test kit". I use one frequently during my warranty claim inspection business. O'Reilly auto parts has the same kit for less cost, but their test fluid sucks like a Dyson vacuum cleaner!
Jerry
