My 2004 Jeep liberty limited smells very hot on back underside what might this be

SOURCE: 2001 Jeep Liberty air conditioner

Check the cooling fan relay. Have a guy(or girl) at an auto part store (AutoZone, etc..) hook up a diagnostic code reader to the hookup uner the steering column dash. I replaced mine, but it was timely and alittle tricky. If you have some tech ability, you can do it, but if not, it will probably be about $350.
If you let the jeep run with the a/c on, look at the cooling fan and see if it cycles on after a few minutes. If it doesnt, it could be the relay, if it does come on, then it could be a condensor prob.

SOURCE: when in 4wd it makes a noise

Is the noise in the front or middle? If it's in the front, it is most probably a wheel hub or differential case bearing. First I would check (or replace) all the gear lube in the transfer case and both differentials.
If the sound is under the middle of the jeep, it's probably a front output bearing in the transfer case.

SOURCE: 2004 jeep liberty thermostat change?

ihave to change my thermostat in my 04 jeep liberty is it hard

SOURCE: Engine smells like rubber burning

Generally that smell is caused by an oil leak that is getting on either the exhaust pipe or manifold (doesn't take much to smell). As far as bottle getting low, I've got a 93 that never stays full but only needs coolant in the radiator about once every two months. Been like that for two or three years and has never overheated. I'm sure there is a small leak somewhere, but I'm not driving myself crazy looking for it. Check all hose connections, and look on the ground after being parked overnight...If it's leaking, something will show up. But if the radiator is staying full, just check it when checking oil level.

SOURCE: it wont shift out of park. what is wrong and how

I don't have a solution, but have noticed that my 2006 Liberty will do this after it rains.