yet another emission and code question

[radioarno]

I'm getting something like exhaust smell in the cabin when the heater is on. I've been getting the codes P0441, P0442,P0446 for the last two years and decided I wasn't going to try to chase down, fuel filler neck, cannister, purge valve, all that stuff. But this exhaust smell in the cabin is new. My mechanic put it up on a hoist and checked it out and said there some leaks near the catalytic converter, and a leak at the exhaust near the muffler.
Here's the question. It seems that the exhaust smell is only there when I have the heater on with the fan. When the heater is not on, and I'm just blowing air temp air into the cabin I don't smell exhaust.
Is the cabin heater somehow connected to the catalytic, so that leaks near the catalytic get into the vent system only when the heater is on?
How could a car manufacturer allow carbon monoxide etc to leak into the cabin of a passenger vehicle? How could that even be possible? [/size]

[andrewclaus]

There are gasketed joints at the manifold and near the muffler. I just had a leak at the muffler flange, and found the flange itself was nearly rusted off. I had to replace a section of pipe to fix that joint. The dealer part would have cost over $1000, but I was able to find an aftermarket repair that fit perfectly for $100.

There is no connection between the CAT and the heat. Perhaps running the contaminated air over the heater core "cooks" the nasty stuff in the exhaust and makes it more noticeable, sort of like how food aromas are more enticing from warmed-up food.

Car exhaust systems are safe with proper maintenance. Owners bear some responsibility for maintenance, especially after 15+ years from the factory.

Check/replace the cabin air filter behind the glove box, and be sure the cabin air ducting is intact. Also, be sure you're not driving with the recirc button depressed. You may also want to get a CO detector.

[joatmon]

i agree that there's no connection between exhaust and whether the heat is running

I have owned several cars where there is a valve of some kind that cuts off coolant flow through the heater core when the temp selector is set to cold.
In your 04 ( and likely 03-08s at least) there is no valve, hot coolant flows through the heater core at all times. The temp control just controls how much of the cabin air flows through the heater core. Is it possible that you are smelling antifreeze and not exhaust? I can see where a small leak in the heater core could cause a smell only when the heat is on. If so, that's good and bad news. Would be good that its not toxic exhaust fumes, bad because I expect it would be a real PITA to change the heater core.