I posted a couple of months ago about an overheating problem. After input from readers, I decided to replace the radiator. Car ran fine and did not overheat, even with air conditioning on. Car began running hot again while idling in traffic so I turned on the heater to help alleviate the problem until I got home. Heater intermittantly blew out cold air while idling and hot air while in motion. Once home, I checked the coolant level which was low. Upon refilling, there was some leakage onto the driveway and I have been refilling every couple of days. Does this sound like a problem with the heater core? Would leakage be associated with this or could it be the water pump? Not sure where the heater core is located so I can't pinpoint the source for this posting. Also, if it is the heater core, how involved, in terms of both time and money is this project in terms of a do-it-yourselfer? Any feedback is greatly appreciated.

I have a vibration/rattling sound on the under carriage of my car. Mechanic was "too busy" to test drive the car & "thinks" it is the bottom cover of the catalytic converter. Said not to worry & just to let it fall off. Does this sound right? Should I have a mechanic remove it? Thanks for your help.