So far the only parts of my engine cooling system that I haven't replaced yet is the pump and the heater core.

Since it cooled off, I've been getting a whiff of engine coolant from my HVAC. it's never very much, and I've check for leaks down at the bottom junction block. There's nothing coming out. Of course I checked everything in the engine compartment. All the pipes, seals, and hoses, were replaced. Things are clean and dry under there.

I'm fairly sure that the core is leaking... a little. I've only topped up a couple centimeters every few weeks. I'm loosing a little bit of coolant, and it's not from the past problems under the hood. Aside from the water pump, and the junction o-rings, it's the only part of the cooling system that I haven't replaced. I checked the o-rings last weekend. I'm not getting greasy coolant on my windshield, but I can definitely smell it.

Is this typical of a leaking core?

Could the over-pressure issues I was suffering back in August lead to heater core failure?


In case you didn't read my series of increasing dire reports, here's a quick summary.
Background
Most of the troubles began when a heater hose blew back in Feb 2011.
I replaced the heater hoses and then the firewall junction block began to leak.
I replaced the junction block and then the radiator side tanks began to leak.
I replaced the radiator and radiator hoses and then the expansion tank began to leak.
I replaced the thermostat, cap, expansion tank, and sensor and then I realized that combustion gases were getting into the cooling system causing it to boil out.

I did a complete head gasket job in September replacing all the gaskets and seals I could access and quickly discovering that the gasket failed... just a little... letting gases and coolant exchange places in the #3 cylinder.

To be clear, the car never overheated. I know the risk there. But I'm wondering if the over-pressurized system claimed one last victim - the heater core.

Sound plausible?