So I just started my first auto mechanic lesson (self taught). I replaced the water pump and changed the valve cover gasket on my 93 Cherokee 4.0L Inline 6. I noticed after putting the valve cover back on that something was broken. Unfortunately I don't know what part it is, and am wondering if anybody could tell me what I need to buy. If you are looking at the valve cover it is at the very back on the driver's side. Thanks for the help in advance.

 

I think based on your year XJ that it's a temp sensor. If I remember correctly it is only for the temp gauge or idiot light on your dash. The temp sensor the PCM or ECM uses is near the thermostat. If I'm wrong about the gauge I'm sure someone will let us know.
Is it leaking coolant?
If not you could go a few days till you get it replaced.
When you do make sure you remove the radiator cap. otherwise you may get a crap load of coolant rushing out of that spot.
I always use some Teflon tape around the threads on those sensors. That way I don't have to torque them down like crazy to not leak.

 

looks like ur temp sensor

 

Yeah that's your temperature sending unit

 

No it isn't leaking coolant and it currently isn't running. I am actually trying to get a new serpentine belt on right now.