Yes, the water pump is usually changed as part of this as the timing belt drives the pump. My guess is the mechanic did not properly fill the system; especially if there are no signs of leakage. It can be a bit of a challenge getting the water pump gasket right given there is such little room to work. However, I would think that link would be fairly obvious.Bob Lincoln said:Does the cooling system have to be opened to change this timing belt? Or is the water pump driven from it, and replaced as a precaution at the same time?