Disco II Overheating when I run AC or Heat

[jlweaver1]

When I run my AC or Heat im leaking coolant and over heating. But if I don't run the AC or Heat, no coolant loss and no overheating. It's been about a month driving around with no coolant loss without running AC or heat. Any idea of the problem?

[Bosnian Discovery]

Help us help you. Where does the coolant leak from? How much coolant did you lose? What temperatures did you see?

The AC and Heat are two completely unrelated systems - the AC uses a compressor, condenser, and evaporator to cool the air while the HEAT uses a mini-radiator-like heater core behind the dash to heat the air. The AC system does not directly use the coolant and therefore should not make it leak. The only thing I can think of is that your expansion tank cap is failing causing the system to either lose or gain pressure when your'e using the HVAC system.

[Disco Mike]

Do a coolant pressure test to find the leak then get back to us.