Cielo Heat problem?

Hello All,

Live in Australian and it can be quite hot.

Now my GF owns a 96 or 97 Cielo. When I first saw it in winter (temps not generally above 20c) it had no water in the coolant filler. So I promptly filled that up. Later in the summer months (temps over 30c) after a while it will stop running and it will not start. After at least 30 to 60 mins it will start. What would cause this? Would she have f'd the seals on the engine? I'm not very good with cars as you see. The problem really happens when the airconditioner is on too. Also when it starts there is white smoke coming out the exhaust which means there is oil getting in there somewhere.

Any help would be appreciated.

Thanks