2003 Dodge Stratus leaking coolant above the oil filter and leaks only when the heat is on.

What I recommend is this. With the engine cold, pressureize the system with a cooling system pressure tester. Most parts stores will lend them to you. It is nothing more than a hand held hand pump that attaches to the radiator. Do this when the engine is cold so you can get under the vehicle and locate where the leak is coming from. Most likely it is a heater hose.