Beginning of spring I noticed the lack of heat in my 99 F150, along with a faint smell of coolant, and my windshield becoming oily. I'm really hoping it's not my heater core, and something simple such as a leaky hose near the firewall, but I'm sure that's not going to be the case. Anyway, is there a simple way of testing what it is, also if it is the heater core, is there a hack of some sort of removing it, besides tearing out the entire dash, it's an old truck, I'm not worry about it looking pretty, just as long as I have heat.

 

Well. I think you already know the answer on what's wrong, even if you don't want to admit it.
And while you can cheat on replacing the blend door/actuator by going through the glove box, yanking the dash is the only way I've seen to get to the core.

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If you decide to replace the heater core, here are some good instructions

https://docs.google.com/document/d/1...sBaH8IdJ0/edit

 

If you want a temporary go around to test it, cut the heater hoses about halfway to the firewall, and pick up a brass heater hose fitting from your local parts place and loop them together. If it quits fogging your dash go ahead and set aside $800 or a weekend to get the heater core done. If you do this lay plastic over your coils and be prepared for the hoses to spill into a catch can or something or a misfire will be in your future. Good luck.

 

I'm wondering how it could be anything other than the heater core.

It only takes 12 minutes + 60 seconds to remove the heater core !!