Recently I’ve been slowly mechanically restoring the old family jeep, a 2000 Sport with 236k miles on it, I’ve done two things in the past week, 1) I pulled the throttle Body and all attached sensors and gave them a very good cleaning with throttle body cleaner, installed a new gasket and called it a day. 2) as part of refreshing the cooling system I finally got around to installing a new thermostat, first two attempts were null and the housing I got from Rockauto was warped as it kept leaking in the exact same spot with two different gaskets (1 fel pro and 1 generic felt) I went to auto zone and picked up a generic duralast housing and a new felpro gasket, put it in and alas no leaks! But as per usual on my xj it’s hard to start (attributed to the fuel pump/regulator not maintaining pressure) after the first few attempts of cranking it it seemed to try to start then made a loud noise, I then tried starting it again and it fired right up but idling horribly and smoky/steam came out the exhaust, I shut the car off and then restarted it and it began running like a brand new jeep, idling perfectly and sounded very healthy, I let it run until 210 then took it for a few spins around the block to get everything moving, immediately I felt that it ran weird when coming to a stop, I came back as I saw the temp gauge climbing, i pulled into the driveway and noticed a good amount of steamy smoke coming from around the valve cover, I shut the car off and pulled the oil cap and lots of steam and smoke started coming out, anti freeze was refilled to proper amount and really have no idea what could have went wrong, im still new to working on cars and so I’m seeking any advice on the matter, could I have messed something up with the throttle body? It has been raining a lot these past few days possible maybe water found it’s way in somewhere?

 

Don't want to jump to any conclusions but since it's a 2000 and given the steaming valve cover you ought to do a search re diagnosing cracked 331 cylinder head. You will find info on where/how to look.
Doesn't sound good.

 

My dad did the headgasket and top end at 200k miles a few years back, it’s always a possibility going to dig into it more tomorrow when I get home from work

 

Did you happen to spray throttle body cleaner down the intake while cleaning the throttle body?

It's somewhat "normal" to have coolant temp issues after servicing the cooling system. Most people don't properly bleed the air out. So long as you shut it off before it got too hot, you're probably fine.

The loud noise... could you describe it in more detail?