re: engine problems

Hi thank you for the reply to my last question(ref.bleeding clutch). I recently replaced my Astra 1.8 to a 2.0 turbo. i have finally started it and drove for 5 to 10mins and the engine is getting so hot that i had to turnthe car off.i checked the water pump and it was ok, my radiator is from the 1.8 motor. iknow it is probably a bit smaller than the 2.0 engine but they look more or less the same, io cant figure out why the engine is getting very hotin such a small period of time like 5min from being switched on. my other problem is that i changed the brakes to bigger ones and when i went for my test drive they didnt work and locked up on me .and when i press them there's a noise like sh;hhh this is when engine is on.may be i put them on wrong ;i just bolted them on and bleeded them after i bled clutch 'i dont know what went wrong and what to check and do; please help me 'thankyou 'adrian.australia