1998 Volvo S40 Water Leakage

Engine problem
1998 Volvo S40 Engine Size unknown Wheel Drive Type unknown Automatic 94118 miles

Hi there, I have a 1998 Volvo S40. Last year I wasn't watching the road and ran over a crate, which smacked up to the bottom of the car, hitting the oil filter. The oil light came on on the dash but I stupidly thought it would be ok and kept driving. Just as I got home the entire motor shut down. Took it to the mechanic and turns out I had seized the motor.

Long story short, it takes them 5 months to fix it (they replaced the entire motor, at a cost of $4.5k)and since I live in New Zealand, we have to wait for the parts to come from Europe. I finally get it back, and it cuts out on me, take it back and it turns out one of the fuel pipes was a bit looser when they were repairing it. So they tighten the pipe, and all good, then it won't start. Turns out that sitting in the mechanic's for 5 months leads to a dead battery. So I replace it and it works no worries.

However now I have noticed, that after driving it for a bit of time, say 20 minutes or so, and then park it, it leaks water below the car. I have no idea how this is happening and where it is coming from, but I always make sure I top up the water everytime I stop. As it is a volvo instead of the radiator being at the front, it is in the back right corner. I am worried that this leaking will cause the motor to overheat. I have a feeling the radiator might have a crack but have no idea what to look for. I am hesitant to take it to the mechanic's because I have already spent so much on it. What do you suggest I do?

Cheers very much

Oh, and it is an import from Japan as well, so it has no manual