Brake Fluid Leak problems of the 1996 Chevrolet Impala

Bosch anitlock brake system pump complaint about the failure of the bosch abs pump on my 1996 Chevrolet Impala. The rear brakes failed on my automobile. I took the car to my mechanic who discovered a fluid leak in the rear brakes and suspected some type of failure within the antilock brake system. Since the cars mileage was only 14,783 and the brakes should not be failing already, he took the car to a local Chevrolet dealership, chuck ohl in chardon, ohio. The chevy dealerships service department diagnosed the trouble as abs pump failure, so they replaced the bosch unit for $1,635 billed to my mechanic. Chevrolet had no reported recalls on this unit and since the new car warranty of 36,000 mile/3 years is expired, I was left to pay $1725. 14 (includes tax) for the new bosch abs pump. Chevrolet service listed the abs pump leaking due to corrosion. I kept the original pump- there is no corrosion on it or any other area of the vehicle. I am the original owner of this car and have kept it garaged every winter from October to may. Therefore, it suffers no corrosion from ohio winters. The brake pads and rotors are in excellent condition. In no way have the brakes been abused on this vehicle. The only reasonable explanation for this brake failure is the original bosch abs pump was defective. I wrote complaint letters to Chevrolet and to bosch. Chevy customer assistance has never answered my letter but I called & they denied the claim because the car is no longer under warranty. Bosch answered in writing. With no corrosion on my vehicle and the abs warning light has never illuminated, bosch's explanation for the abs pump failure suggests the brake system absorbed moisture. They also state the brake fluid should be replaced every 1 to 2 years, "like many vehicle manufacturers include in recommended maintenance schedules. " I have carefully checked the Chevrolet owner's manual delivered with my vehicle-changing brake fluid is not mentioned.