Coolant loss 2003 TDI 130

Hi - my dad has one of the above and it has 74K with full VWSH.

It has been standing for about 4 months with occasional start ups but now he needs to start using it again.

When he started it the STOP light illuminated and he did just that, pronto.

He topped up the coolant which was low and then started it again.

After 15 secs the light came on again and the coolant was rolling down his drive from under the car.

I presume a pipe has burst/cracked but any ideas where the leak may be coming from or what the cause may be?:confused:

Cheers

Stu