okay so i bought a 1990 jeep cherokee with a 5 inch lift, 33's and supposedly a good running engine. its a piece, but hey it was 500 bucks so i didnt care. i got it home and drove it through a trail about a quarter of a mile n the woods and back. when i turned it off i heard a hissing under the hood. water/antifreeze was spewing out of the clear resevoir in the back left of the hood. all the water pipes were hot. also the temperature gauge was high, around 230-240. now everytime i crank it up n drive it for more than a few minutes it does that same spewing thing and i dont want to crack a head or anything. i replaced the thermostat and it continued to do the same thing. what should i do next? thanks for the help!

This is a very common problem for this year,depending on how much you have to put in it there a couple of ways to go. Fix what you have or change it to a 91 or later style system.
As far as this system goes the plastic bottle is the main problem,they get hot and almost always have a hard time sealing the cap again,also is your electric fan coming on when it reaches about 220?is your a/ cond in the front plugged with debris,is your radiator plugged?is your water pump working?is the mechanical fan working? there is a number of things it can be,need to isolate it. Your radiator could also be plugged inside.
The other option is changing it over to a 91 or later system,they do not have the bottle and exsperience less problems

honestly, im not sure what all is workin. i got this yesterday so i havnt had much time to look at it. i know the fan is running and apparently the guy who had it before me installed a second fan beside it that is also working. my next plan i guess is to get a water pump because it doesnt seem that there is any water in the lines. and any water that i put in that plastic bottle backs itself up to the top and spewes out until its out of water again. based on how i TRIED to describe this ha, what would be the next thing you would replace or check? thanks man

From what you are saying I would first make sure you have plenty of water in it,you will need to burp it,fill up the bottle,put the cap on and warm it up to about 200,let it set and the air will vent out to the bottle,you can also open the cap a little do speed things up,as the air escapes the water will enter the block and you will need to replace it,do this a couple of times until the water stays in the bottle. At least this is how I have done it,then check the pump once it is warmed up by squeezing the upper hose and see if you can feel water flow through it,if both fans are working that is where I would start.

sorry about the dumb questions, but how do you burp it? ha or is that what u described after u mentioned that?

That is what I described,there are other ways,some threads on here can exsplain this also,there are no dumb questions.we all start somwhere.

i have an 89 that had the exact same problem, turns out the smarty pants before me put the tstat in backwards haha so i changed that, still overheats. there is a sweet spot on the cap, fiddle with it and if you do find that spot mark it. also for the closed systems the rads are pretty bad right from the get go, suggest a rad upgrade. lastly try drilling two holes in your tstat at 6 and 12 o'clock. If all else fails change over the whole thing

okay thanks guys. ill try burpin it in the mornin and let you know tomorrow if it worked or not. also the guy said that this jeep sat for about a year. not sure if that would tell u anything..

Whenever a veichle sets for that long it can develop alot of rust in the block,you be wise to flush it out,after you have cycled the engine temp a few times from cold to hot .this will cause alot of the scale to come loose.
The other thing about these bottles is,whenever I have had them get hot,i made the mistake of putting the cap on when it was hot,I would strip the cap everytime. I always carried a spare bottle,some have used metal ones with success,I just changed my over to a newer system from a 91,no problems since.

i had to replace my coolant resevoir because mine had the same problem. if the cap doesnt tighten down alot then you might want to try that

how do i cycle the temp? and flush it? or is there a link that i need to go to to find that out?

okay yea ill definitely replace that

Heat it up to about 200 then let it cool off to ambient,then do it again,the rust or scale in there will let go from the exspansion and contraction of the metal,once you have done that a few times go to the auto parts store and get a flush kit,and yes there is a thread on here for everything to do with xjs,just look.