LOS ANGELES, April 17— The actor Arnold Schwarzenegger had a faulty valve in his heart replaced on Wednesday, and his doctors said today that they expected a full recovery from the elective surgery.

''I've never felt sick or had any symptoms at all,'' Mr. Schwarzenegger, 49, said today in a statement, ''but I knew I'd have to take care of this condition sooner or later.''

Mr. Schwarzenegger's doctors said they foresaw no need for medicines or changes in his life style after the surgery.