We have a 2005 C240 that worked fine until 8/11/08 when it stalled and gave up and we took it to this dealer to be fixed, they changed the catalytic converter and gave it back to us on 8/13/08. Then while driving back home that night we heard a knocking sound which we had never heard before. The very next day we took the car in again and the next day the dealer said they found water in the oil of our car. Which could have gotten there only by 2 methods, either from within the engine or from driving in water. Our engine was hydra-locked and would have to be replaced at a cost of $9000 to us which insurance would cover.We contacted insurance and they sent an adjuster and he determined that there was no evidence of our car having ingested any water through the intake. Our dealer did not do anything the next few days understandably because of tropical storm fay. On 8/27 they told us that we have a bent piston in the engine. It has occurred due to external influences and will not be covered by warranty. The last people to touch my car was this dealership, so if anything it is their liability. We could wither pay $3750 to get the engine opened and determine if there is a manufacturing defect which most likely it is not or just pay $9000 and have them install a new engine.If this is not unfair business practice I don't know what is. My car is under warranty, if there is something wrong with the engine warranty covers it. The last people to touch my car was this dealership which is when the knocking sound started, it is their responsibility to fix it with no cost to us. I am very disappointed in this dealership.