Volkswagen: 1998 Jetta GL 3rd water pump..., water pump, antifreeze

Question
I have a 1998 Jetta GL, 4.0, Manual at 88,000 miles.  I rear ended somebody about nine months ago and did realize I had put a hole in the radiator and ruined the water pump.  I drove on it for a week before it overheated and took it into my mechanic.  He replaced the water pump and radiator, but one month later the water pump was leaking and he replaced it again.  I drove it another month and the water pump again started leaking.  My mechanic replaced the water pump and the head.  I have now drove the car for about 5,000 miles and the water pump is again leaking antifreeze.  My mechanic can't figure it out; he thinks there might be a crack in the block, but isn't sure.  Any ideas would be greatly appreciated because I'm about to drive the car off a cliff.
thanks

Answer
First thing first Jason... Do you mean your car is a 2.0 liter gas motor? (not a 4.0)  Also,...I've never seen a hole in a radiator ruin a water pump.  HOWEVER, if you overheated the engine then MAYBE the waterpump warped and started leaking.  That said, is the water pump leaking from the pump half/housing half or from the mounting point at the engine block?  Do you know if the entire water pump was replaced, (with the housing) or just the pump half?
let me know these answers and we'll go from there.
thanks,
shad