Refusal of insurance Your assessment

2 questions: New car 2-3 months old, upper middle class, 4,500km. Car drains during the passage in an underpass, stands 1m high in the water. Engine has water impact. Car is insured. Insurance wants to pay drying, but not the engine damage. Reason: Production error. New car (in case of damage entry) 1 day old, 220km, luxury class with genuine leather, fully comprehensive, car was examined by the insurance because of the high purchase price and valuable accessories and special graded. Car drains due to failure of the pumping system in the underground garage, stands 3m UNDER water, mix of sea water and rainwater and that over 3 days because nobody notices it (owners and other tenants in this parking hall in holidays, the caretaker noticed). Insurance only wants to pay “repair” but no new car. The car stands completely disassembled at the dealer, it forms rust and the seats can no longer be saved according to dealer, the whole car moderates and stinks. The manufacturer does not want to give a guarantee on rusting after drying because it is not sure that all water is out and no further damage has been caused. Can the insurance companies do that? If so, why?