Radiator Issues

[tbegin]

Hi all!
I have a 99 Passat, around 110 K miles - we bought it used a couple of months ago. About 3 weeks ago, we started leaking coolant and overheating - took it to a European car mechanic, and they replaced a couple of the hoses. However, now we supposedly have a crack in the radiator tank, that wasn't there before because the built-up pressure in the tank was able to escape through the leaky hoses.
Anyway, my Dad was going to seal up the crack for me this evening, but mysteriously, he was unable to get it to leak anymore, even though he had it running for close to an hour and drove it around. As I just had to have it towed on Saturday for leaking, overheating, etc., I'm a bit puzzled by this.
Anyone have any suggestions?

Thanks!

teri