It all started yesterday afternoon on my way home from work (It's around 15km) when I noticed mid way that my temperature gage was rising. It never hit the red but it stabilized at about 3/4 before the hot section. When I was about 1.5-2kms from home I started to notice a strange clicking sound in the engine and when I stopped at a red light, it stalled. I was able to started up again and barely managed to get the rest of the way home as the motor was becoming louder and the gas pedal heavier.

When I got off the car, I noticed a strange sweet smell coming from the engine and it was steaming. I called the NRMA and the guy came and told me that it was overheated. He added coolant water and ran a couple of tests with the engine everything looked good and it maintained a cool temperature. At this point the smell had stopped and there was no leaking at all so I thought that the problem was solved.

The next day I drove all the way to work without any issues whatsoever, the engine held a cool temperature and I arrived normally. However by the afternoon, half way back I noticed the car overheating again only that this time it was much worse. The car stalled on me repeatedly but with some effort I managed to restart it until I got to the nearest service station (not even a KM from the first stall) and allowed the engine to cool for a few minutes and bought some coolant as advised by the NRMA the night before. I open the water lid and poured coolant into the engine. Despite the engine being off for some minutes, I could hear the liquid bubbling and stuff, I figured that it was because the cool liquid was reacting with the hot liquid inside.

After a while I noticed a bit of water leaking from under the car, I figured this was my fault as I had spilled some water while pouring the coolant. I then tested the engine and it started off just fine, no strange sounds or anything. I tested it a bit and it seemed alright and maintained a cool temperature. I managed to get home without a problem and the car drove very smoothly.

However once I stopped the car, I noticed a strange hissing sound coming from the engine that lasts 15-20 seconds or so before going away. I tried restarting the car and turned it off and the sound happened again, it seems consistent now. When I got off the car, I noticed that the car had continued to leak what appears to be coolant and there is a slight sweet burned smell coming form the engine.

Anyone know what is going on and if it would be expensive to fix? I certainly hope it's not expensive as my car is not really worth investing any more money on and I don't want to go as far as buying a new car.

Any help is appreciated.