If you are loosing two litres then you should see water and oil mixing togethr in the rad and in the oil dipstick. You can also check for choclate milk shake type paste under the oil cap. If you don't have such symptoms then you have a leak.
I replaced the Pump & T-Belt , costed me around 4k total. If your car is heating up badly then stop driving it because if you havnt yet screwd ur gasket , you u will eventually then u will have to replace the gasket , get the head milled and fix the reason for leakag.