Our 95 4.0 Xjs .just installed a thermostat due to not getting to temp. burped the system. We drove about 100 miles and lost interior heat next morn had heat , lost again around 100 miles . Ant thoughts ???

 

If it's the same as the V12 the heater tap is a known source of problems. I assume it's the same as the 12 and with AC full cold heater tap closes with vacuum, any other setting the tap will be open. I think is a good place to start.

 

It appears to be in the open mode. Thank you for your response.

 

I have heard of problems with the vacuum dump valve. I've heard of leaks with actuators also>