Jaguar Repair: Heater valve, heater control valve, vacuum line

Question
Hi Howard. 83 XJ6 has gurgling sound in the heater when revs are increased slightly, then goes away. Happens the same every time. Possibly air in the system. Parts supplier advises heater valve is "always open". Vacuum line doesn't seem to change the valve when heat is ON or OFF.
Any clues ?  

Answer
Hi Ray,
If the cooling system is not full it could be air in the system but if it is full it is not likely air as any air in the system would quickly be purged out of the system.

Check the vacuum line for vacuum then hand operate the heater control valve as they are noted for rusting solid.

Howard