If the coolant was low and you had to add some, but there's no apparent leak, that suggests it is sneaking out through a leaking head gasket. There are some different tests that can be done to find where the coolant is going.
The first test is a simple pressure test. A hand pump is used to pressurize the system, then you watch the gauge to see if the pressure drops, and you can search around the engine for signs of leakage.
The second test involves testing for combustion gases in the cooling system. If gases can get into the coolant, coolant can go into the combustion chamber too. The tool is a glass cylinder with two chambers partially filled with a special dark blue liquid. Air is drawn through the cylinder from the radiator. If combustion gases are present, the liquid will turn bright yellow.
The third test is to add dye to the coolant. After driving for a while, you search with a black light to locate the source of the leak. The dye will be bright yellow. If the head gasket is leaking, the dye will show up inside the tail pipe.
Tuesday, May 3rd, 2011 AT 3:12 AM