I have a 2001 Jeep Cherokee Sport woth 150,000 miles. All of a sudden I'm driving down th eroad and the check guages light comes on. I pulled over, found reservor empty so I filled it, let it cool and then drove home. Had to shut it off 1x on way home because it got hot again. Once home there was hissing and steam coming from the top back of the engine. I let it cool. Then took radiantor cap off, it was very low, after adding a gallon I could see a stram pissing out the top back of the engine a few to maybe 4 inches below the valve cover. Tried using a mirror to see but can't really see the back side of the engine. Is there a freeze plug back there or do I have a crack in the engine. No smoke, oil is fine! Hopefully someone has some good news! Lol

Inline 6 cylinder?
You may not have gotten lucky this one... still it's not terminal.
If you're describing the location correctly, you have probably found a leaking cylinder head gasket at the rear of the head.
This needs a closer look. Get is checked before it becomes a larger problem.

Ya, it's a I6! Is that a exspensive fix if it's cought early? Thanks for the help!

Price will vary from one region to another so I cannot say what you will pay.
Likely between $50-100 for parts and expect about 5-6 hours labor (again this rate varies), depending on what needs done to successfully remove the head: i.e.: rust or broken bolts, etc. Also you may need the cylinder head serviced, which can add significantly to the total cost.
Call around and explain what's going on. Ask about warranties and technician credentials, too. Some shops can do this type of repair quicker and less costly than other.

****edit**** use the iatn shop finder in my sig line if you're not sure who to trust.