The "business end" of the thermostat that senses the temperature of the coolant sticks into the engine. As the coolant in the engine heats up, the thermostat opens allowing coolant from the radiator in to cool down the engine.

After a period of time, there will be a build-up of deposits around the point where the leak is. That could take weeks or months. That's why people use the leak detecting dye to locate a leak. You can buy or rent a radiator pressure testing kit at your local parts store to test for leaks. With a cool engine/radiator, you pump up the system to operating pressure (about 15-16 psi) and watch it over a period of time. If the pressure falls, you have a leak. It won't tell you where the leak is, however. That's what the dye is for.

 

Hmm so in this car ..its vice versa....normally thermostat opens and allow hot coolant to go to radiator to be cooled down but in this case...thermostat opens to allow cold coolant to go in to engine ...correct?