Hey guys i just got a an 88 xj pioneer 6cyl. And its over heating, its not the thermostat, cuz it has been removed and replacing that it is not an option. The stupid overflow tank is operating somewhat those stupid lines coming off of the overflow tank that have that metal t pipe wher clogged but i took care of those but now i think taht the heater core is bad how do u bypass the heater core?

 

plug heater core will not cause over heating sounds like a good flushing of systems needed if lines to tank were plug radiator most likely same way seeing how tubes are so small.

 

So I had to chase overheating on my '88 as well, finally got everything figured out, when is it overheating while you are idling, on the highway, going up hills? How many miles on it?

 

Are you not running a thermostat at all??