I read a post somewhere that the heater core will sometimes fail early if a head gasket is going out, something about too much pressure in the cooling system. Might want to check into that. I also read that some trucks have restrictors in the heater hoses, maybe yours needs one?

 

Do most of the older f150s need this? Any other symptoms other than antifreeze smell? Those YouTube videos were very informative

 

Correct. You can test this with a hydrocarbon test. To determine if there are exhaust gasses present in the coolant.

 

Well, because it was raining in Az at the time I was smelling engine coolant in and around my truck and the fact that my heater and defrosters were not working, I just assumed that my truck was actually leaking coolant. It is not yet leaking, but I can defiantly smell coolant inside the truck. The shop said that they were able to smell it as well, but could not find any leak and my defrosters were working at the time they tried them (Of course the thing works when I need it to NOT work). I called them today, and they are trying to diagnose the problem because all they were able to find was the smell . They said that they ran some kind of pressure test for the heater core, and that there was not any extra pressure going inside the heater core (so they do not think that there is a cracked head gasket), but I did recommend the hydrocarbon test that TOYZ recommended (Thanks by the way).They will call me back later if they find out more. Thanks for the recommendations everyone, but is there any other reason that anybody can think of as to why this keeps breaking?
Thanks everyone!
And sorry laneman, I am beginning to feel like I stole a thread...oops

 

I am 99% sure it's your heater core. I've had a number of them go out in my lifetime. Every time I smelled antifreeze inside the cab it was a bad heater core. I would not wait too long, it will eventually leak enough to make your blend door actuator go bad

 

Well, I got the truck back, and they are pretty sure it is the heater core, but they are not positive. They could not find exhaust gasses in the coolant, but what scares me is that they said that they were able to smell antifreeze, and see some smoke coming out of my exhaust, and they only noticed this ONCE when they had it. I checked this myself, and did not see any smoke or smell coolant from my exhaust. I have had my truck for almost a week, and have not noticed a problem. My defrosters and my heater work fine.
What is going on????
Thanks for the help again everyone!