Bought an XJ this week for a bargain.
Shes lifted and has a ton of mods.
I anticipated having to do some work to it.
I did the thermostat and gauge sending unit, the gauge is still bouncing like a fat kid on a trampoline.
I bled the cooling system for 30 mins and am still getting bubbles, theyre not consistent but Im thinking head gasket.
It was overhauled a few years ago, new pistons, connecting rods, water pump, etc etc.
The thermostat was stuck closed and it was dying after about 5 mins of driving. Then it would start back up and buck like it was starving for fuel. I dont know if I got it fixed or what exactly was causing it. Im assuming it was overheating and causing a misfire. Any ideas will help. I dont wanna open her up if I dont have to!
I got it for $1500!!!

 

Do a compression test, examine the oil filler cap for cream, check the radiator for bubbles, that should give a clear indication if the head gasket is gone

put an OBD2 code reader on it in case its an O2 sensor or some other engine code is set