leaking water

my 01 malibu has been leaking a lot of water from the heater core condensor hose. I know it's normal to drip, but last week it was dripping a lot of coolant from that hose, and I was getting steam coming through my defrost vents. I thought this was caused by my p420 trouble code, so I replaced the o2 sensors and reset the code, which didn't fix the 420 code (the light came back on a couple days later,) but it did fix the coolant leak and steam. But now after the car has gotten to temp and I turn it off, the condensor hose leaks more water than I've ever noticed in the past. Even though it's working ok now, I wonder if the extra water leaking means I damaged my heater core? And I wonder why an exhaust problem would seem to affect the core. Any ideas?

P0420 is a catalytic converter performance below threshold (bad) code. Your replacing the O2 sensors and still getting the code more or less confirms that your cat is bad. The water leak is just a coincidence (when it rains, it pours).

I already replaced the cat with a universal, the sensors were the last major part that should have fixed the problem, but they didn't :frown:

check the wiring to the sensors

Tomorrow I'll check the voltage output of the sensors, I'm also going to change the spark plugs and wires, replace the thermostat, check the exhaust system for leaks, replace the coolant temp sensor, and do a flush and fill. Any other ideas of what might cause a P420 code?

Also does anyone have any pointers on how to thuroughly check the exhaust system. Are there any common leak points on this exhaust?