So I have a '95 XJ Sport that was leakin coolant from the Heater Control Valve. I tried replacing it, and the leak somehow got worse with the new part. Tried it again, same issue. I kept reading about HCV deletions and I figured some heating/AC issues were nothing new so I tried deleting it with heater hoses. This stopped the leaking issue and I thought it was good until I took it out for a test drive and now my coolant temperature is through the roof? I've never had coolant line issues before like this. Is there a chance I hooked up the system wrong? Or is the HCV delete just not a good idea.

 

Probably need to burp out the air that got in there when you were messing with it.
if the heater valve delete caused the problem all 97+ xj would overheat

 

Well, your heater hoses are connected backwards. The outlet from the thermostat goes to the lower port on the core. The upper returns to the water pump. It's possible you have an air bubble trapped in the core. Don't think that would cause overheating but you might have reduced heat in the cabin.

Make sure your overflow tank is topped off. It does take a few heat/cool cycles to purge the air in the system.

Make sure you capped off the vacuum line that used to go to the heater valve.