Scottish Elises

During the last couple of weeks, I've noticed that, when idling, the heater just blows cold air, but as soon as I start driving, I get hot air.
The temperature gauge also rises quite quickly when idling, but soon comes down again when driving.
It looks like there's plenty of coolant, although when cold the expansion tank is empty, but when hot, it's full
Could this be due to air in the coolant system and if so, how do I get rid of it?

PS it's 2007 S2 (Toyota engine)

Cheers

Sounds to me like an air lock or dare I say it a pressure buildup in the coolant system If it were mine I'd just fire it to Craig at CMC and make it his problem? Pretty sure they'll have come across this before mate.

Hope you'r well

Mark!

(On all counts)

Bleeding the system will be the place to start for sure. The question will be how the air got in there (where did the coolant go?).

Cheers,
Robin

Thanks all.
So, it does sound like an airlock.
Due a service in a month or so and I've still not seen Craig's new place, so a good excuse to hand it over to the experts and check out the new premises at the same time.