@toximus
I bypassed my heater core last July due to a leak but didn't have the replacement heater core installed until February. That gave me ample opportunity to observe temperatures with the heater core in and out the system. I can confirm that the absence of a heater core in the system did not have any adverse effect on total cooling even during a 10-day heat wave of 110*+ temperatures. My temperature gauge was typically at 210* before the heater core leak, showed hotter between discovery of the leak and the heater core bypass, returned to the typical 210* after the bypass, and has remained at 210* since the heater core replacement. Even though most TJ's have a dumbed down gauge that does not show small changes in coolant temperature, the fact that the gauge remained relatively constant is an indicator that any difference in coolant temperatures with the heater core in and out were also small enough not to be a concern.
