iv had my xj for a year now when I got in I put in a new rad and tstat the cooling system has been good up till this past weekend I took it out on a long drive 150 mi round trip on the way back temp started to go up over 210 I would say near 230 the ac fan was on when I got home went to work today and temp was at 210 to 220 now this is going down the road at 55 up till last Friday temp never went over 195 driving where do I need to start looking I might put in a new tstat this week xj is lifted 4.5 and has 32s

 

Not to beat a dead horse but use the search function before you make a post. This issue and probably 100 more that you will come across have been talked about to the moon and back.

That being said, XJs are notorious for their shotty cooling systems. You need to round up $3-400, maybe 500 bucks depending on which routes you go and whether you do it yourself or pay someone. You need to start preparing for a full out overhaul if you want to do it properly.

And free hint, "search" my threads. I believe I started a half hearted one listing everything I did.

 

replace the thermostat since its cheap and flush the heater core out