Coolant System Pressure Test
Use a radiator pressure tester to test for leaks. Install the tester on the neck of the radiator or the coolant reservoir, and pump until you reach the pressure marked on the radiator cap. Check around the engine, hoses, and radiator for leaks. Check inside the floor and console area for heater core leaks.
If the engine is started with the tester installed and the gauge quickly increases past the recommended psi, the engine has compression leaking into the coolant jacket. This will result in white/gray exhaust. This may be due to a blown head gasket. Aluminum heads warp from heat; cracks can form in the cylinder head or the engine block. Always perform a block test to verify any suspicions.
The radiator pressure tester can also be used to check the radiator cap. There are many different types of adapters depending on the application. Install the cap on the tester and pump to the recommended psi. If the cap looses pressure, it will be necessary to replace the cap.
Hard to find coolant leaks can be diagnosed using a dye penetrant. Just add the dye to the coolant, heat the engine to operating temperature, and use the black light to inspect suspected areas for the telltale green fluorescent color.