 Question
I own a 1998 Ford Expedition. Recently, I started smelling an odd fishy smell coming from the vents, which turns out to be the antifreeze. The vehicle was given to me, and it runs great, however I believe that the antifreeze was never dumped and replaced because instead of it being clear and greenish its brown and smells horrible. After doing some research I'm lead to believe it's my heater core, but my heater still works, my windows arent fogging up, there's no leaking fluid in the interior of the vehicle, the radiator and coolant overflow are full, and I smell this aweful smell when I'm running cold air as well. Could it still be my heater core, or could I just need to replace the antifreeze? Either way I'm going to get my radiator flushed tomorrow and see if that helps. My check engine light is on, but sometimes turns off.
So what do you think? Bad heater core? Or is it just plugged up or is it because of the dirty/old antifreeze.
Any input would be greatly appreciated because I've seen how much work is required to replace a heater core on this vehicle, and I don't have the money to take the car to a shop. | 
