1989 1.7 litre 33 overheating help please

[dirty harry]

hi this is my first post and i hope u can all help
i have recently bought a 1989 1.7 litre alfa 33 ( possibly a green cloverleaf one as the car was debadged when the previous owner resprayed and i found in the bag of bits accompanying the car the 33 1.7 badge that also had a green clover leaf attached) this is my first car and i absolutely love it however it has a overheating problem. i live in the adelaide hills and am completing yr 12 in the city it is great going down the from the hills(the beutiful norton summit road for those who know the area a great drive too and from school) however in the afternoon coming home up the hill it over heats. the first time this happened the fuse between the thermo switch on the radiator fan and the battery had completely melted into what looked like a hard boiled sweet, this obviously stopped the fan from working so the car over heated. i replaced the fuse and the thermo fan worked fine (this was about a week ago). today coming home from school the red light on the temperature gauge on the dash come on so i stopped the car. i made it home and both fans are working fine however i was reading the workshop manual that i downloaded and the recommended temp for the fan to come on is around 90C so i went into the drive way reved it for a little and according to the temperature gauge on the dash it was around 90 and the fan was not on it wasnt till around 100-110 degrees that the fan came on . this is an infuriating problem because when i was taking this car for a test drive there was no sign of overheating and the fan was coming on at what i assume was the correct temperature. also today when i was on the side of the road waiting for it too cool down there was coolant spraying from the seal between the two halfs of the coolant resevouir however i am sure that before today it was full with coolant so the coolant wasnt low and hence i am assuming low coolant was not the reason for overheating.
i think this is all any other things i need too add for diagnostics please tell me and i will gladly add.
i hope someone can help me and any help would be greatl appreciated.
thanks in advance
(P.S. does anyone know how i can chek if this realy is a gree cloverleaf or weather it is just a badge. thanks)

[dirty harry]

found the problem the coolant resevoir was bodgely patched up with silicon and it busted the seal so it lost its coolant. (despite my original statement ) so all is good now i think i just gotta find a resevoir but i think i got one lined up thanks too all who looked. however i would still be interest too know if anyone could tell me how to identify if it really is a green clover leaf. thanks anyway