So I ripped the heads off my ranger last weekend and took them in to be milled and pressure checked. Turns out with the pressure check and inspection that my heads were bad. I had a crack between the intake and exhaust valves on both the number 1 and number 4 cylinder. Bought new heads from the machine shop and am getting them when it starts snowing. Now I have a slight delay in getting them torqued the rest of the way and putting everything else back on so I can start driving my Ranger instead of my wife's car.

 

My '94 4.0l also cracked a head, #4, same place, between the valve seats, pretty common if they are ever overheated.
My water pump gave out(I knew it was leaking) and I just had a few miles to go to get home.................expensive goof, if I waited an hour and let if cool down I could have made home and saved a few hundred $$$, in the price of the new head and cost of head gaskets and time.

I have heard of them just cracking, but I am sure if you went back far enough in the engine's history you would find it had be run hot at some point.