Hello, when running my AC on it leaks Collant, I went through a whole overflow bottle (2 Litres) in half an hour of driving in my 1989 3.9Lt multipoint EA Falcon.

Ac shouldn't use cause coolant lose replace your radiator cap.

easy one run it in the yard with air con on and look for leak when it heats up

Seems to be the problem ^^^^^^^^^^^^^^^^^^.

maybe also the heater core if its loosing coolant. Check also if heaps if water is coming out of the aircon drain hose.

Good point but he says it only looses coolant when the AC is used, another cause could be either stuffed thermostat or a partialy blocked radiator.

Yeah but im thinking if he adjusts the temp when the ac is on the heater tap will open letting in coolant to the heater core.

He's in perth I dont think he is adjusting heater temps right now. Unless the heater tap itself is stuffed.

Let's see - does the car still have a clutch fan as they originally come out with?

Does the temp rise a lot on the gauge when the a/c is run? Even before the water starts to leak out?

If the car get's too hot when the a/c is on it will loose coolant thru the overflow (expansion due to heat & pressure). First thing to check is the "radiator cap", 2nd is the thermostat. 3rd would be to remove & reverse flush the radiator, and blow any crap clogging the fins up on the outside out of it.

Also, consider the clutch fan for a minute - could it be on the way out, not spinning fast enough to cool the coolant, causing the car to get hot & loose coolant?

My clutch fan started to die on the eb, when you spun it by hand it was very easy to spin, and it didn't spin fast enough when the car was idling, causing it to get rather hot when stopped. I converted to EF thermos, but an easier solution is to replace it with a good clutch fan if it is buggered.

Cheers

ToranaGuy