gordo, from the description of your problem, i had exactly the samething. Km wise is close to yours. Coolant were leaking everywhere. was dropping down quite quick. Checked all hoses and seem all ok. water pump seem to be on the way out as i can see some coolant leaking from it. did a compression test from the radiator and it appears loosing pressure. hmmmm, screw the radiator cap on really tight and since then it seems all fine. weird i know but it could be something really simple like the radiator cap not screwing on tight enough. after a few months down the track, coolant didn't drop at all, water pump seem to be ok miracle i'll say..