Simon151191

Hi all, new member here as i just bought my first suby last week. Its a 2004 impreza rx so 2 litres of n/a goodness . When i bought it i was told it had a slight overheating problem but for the price and with some mechanical knowledge i thought it should be fine. On the way home (about 15kms) i had to pull over twice as it got hot and spat coolant out of the overflow bottle when stopped/moving slowly in traffic so when i got home, i let it cool down and pulled it to pieces which is where things got a little interesting. The bloke i bought it off assured me the thermostat had been replaced and there had been tests done for exhaust fumes in the coolant and compression tests a month ago, however when i drained the coolant, it was no more than slightly red and gunky water with tiny silvery floaties (chemy weld?). I pulled the thermostat and dropped it into boiling water and it opened but thought it best to replace it anyway along with the radiator and cap due to poor flow and staining at the bottom tank. Of course with that came a massive flush of the engine. Filled it back up and bled it as best i could without a funnel. Just warming it up in my driveway the bottom hose was still staying cold and the radiator was only luke-warm but i read that these need to be driven properly to get the bottom hose warm so decided to take it for a drive today (about 10km) and it started getting warm again, But it was no longer over filling the overflow bottle. Is it possible that there is an airlock or do you guys think there is something a little more sinister going on? Im thinking maybe water pump, which would explain the floaties, or dreading head gaskets. Let me know what you guys think, any help is very much appreciated! Thank you for your time