'95 F150 4x4 302, 70K, at
Have been losing coolant for a month or two, about 16-20oz. a week. I noticed green liquid (obviously coolant) coming out tailpipe when I shut the engine off. Not much, only a few drops.
The engine runs fine, but only getting 10-12 mpg.
Is this a head gasket? How expensive is this going to be to fix. How do you tell if I have cracked or warped heads?
Thanks for the help.

 

Well, to tell if cracked or warped head, need to take it apart to find out, unless someone else knows another way. A compression check will verify your problem, it would be worth doing, and may tell something if there is a pattern to what cylinders are way low. It will also tell which head needs to be pulled off. If you are getting coolant into a cylinder, you may be getting oil into the radiator too. Also, if coolant gets into the oil, it reacts with the oil and creates a black goo that can crud up an engine big time. I wouldn't run it that way for long. 302's are pretty good engines, 70k for those problems seems unusual to me. I would start with a compression check, then only fix what is wrong. No need to go overboard with big $$ engine rebuild with only 70k on it if it doesn't warrant it.
One more thought, if you engine has an EGR cooler, that cools the EGR by running engine coolant through it, if it leaked, coolant could get sucked into intake when running, maybe into exhaust or intake when parked. A simple thing to fix. Compression would be fine if that was the problem. Just a thought.