What is the Piston's and what does it do?

If the pistons have failed then your better off looking for a used engine as piston replacement will cost more than a used engine

the pistons play basketball in detroit. in your engine, they are the parts that get pushed down by the expoding fuel to turn the crankshaft that ultimately moves the car. many things can be wrong in this area but what your mechanic is trying to tell you is the main part of the engine needs repairs which is usually done by replacing the entire engine. by the time your done you'll still only have a 94 vw.

The pistons force the crankshaft to rotate due to an explosion of air, gas ,and a spark from the sparkplugs in a combustion chamber that is in each in this case 4 cylinders.These are internal parts that require experienced mechanics. so it's fair to say These parts can be replaced in some case's repaired such as ring replacement wrist pin etc. Hope that answers for you....