RAMU, Its your FAULT because If the Car become Overheat and you see the TEM BAR high you have to stop the car on the Spot. its just need to FIX the leakage.
but after you keep drive the car mean the HEAD GASKIT is gone.
normally its cost 4 to 5 on the small sedan car+ delay time.

So you are the One.
if you are Honest please repay him some Extra and go out of his shop safely.