my old radiator had a hole in it, it was going to cost 1400 to get a new one so i went on ebay and got another and fitted it myself now it is running hot? it has plenty of coolant in it, i took it for a test ride and it was okay then started running hot, i noticed the reserve tank went empty so i checked the radiator cap and refilled it but it seems to be running hot still normally sits on 46deg now it is rising while to 100deg not sure what the problem is can you help me ?