That really doesn't sound good. However if the mechanic admitted that they did something wrong I hope they are doing the work for free or a very reduced price.
To explain it a bit better, The water pump on that engine is tucked into the engine and is behind the engines timing belt and driven off of it. In order to change it you need to remove the timing belt. The timing belt is what connects the crankshaft at the bottom of the engine to the camshafts inside each cylinder head.
If you look at the first image you will see the timing belt, it has some red lines on it, the tensioner and adjuster for it are circled. The adjuster is likely the part that wasn't tightened properly. The yellow area is the water pump.
The next picture shows the cylinder heads and where they are on the engine. The last pictures show the heads in exploded views, the yellow items are the valves that bent, there are 4 of them in each cylinder as in the last image.
When the timing belt loosened up the camshafts would have moved out of time with the crankshafts. That engine is what is known as an interference engine. That means there isn't room in the combustion area of the cylinders to have the piston and the valves in there at the same time. Something has to give, it can be the valves that bend, it could even break them and then push them through the piston. Until it's actually taken apart they won't know for sure. If it only has bent valves, then replacement cylinder heads could repair it, if there is more damage then a replacement engine would be a better option.
This video shows the timing belt and water pump change on an engine just like yours. This one was done correctly though:
This one explains the issue a bit more, however your car only has single camshafts so the valve to vale issue shouldn't happen:
If you have more questions just ask.
Images (Click to enlarge)
Wednesday, April 21st, 2021 AT 2:33 AM