I had my intake manifold gasket changed and a full tune-up done 1 month ago because I was leaking antifreeze directly out of the gasket. Now 1 month later, I had to change the water pump. Because it was leaking antifreeze onto my serpentine belt and that broke as well. When we pulled the old water pump out it was not turning it was froze up. So I know that was a problem, but now, we pulled the valve cover off and none of the valves are wet with oil. And my car makes a loud knocking noise. Can you please help me with what this could be? I am at my wits ends with this car and it's engine problems, one after another?