Carol Greenwald is stepping aside for three months as president of the National Consumer Cooperative Bank, and a bank spokesman would not say whether she will remain as president after that.

A bank director who asked not to be identified said yesterday that she will be "phased out" as president. Richard A. Gross, a bank vice president, said there had been no decision or understanding among the directors to replace her. "Officially, there is no change in her status," he said.

According to one source, her contract as president expires Jan. 31, 1983. The director said that the board had voted last month not to renew her contract but later rescinded that decision at the same meeting. At a meeting last week, the board decided to offer her 18 months' additional work at the bank as a consultant, according to the director. Gross confirmed that she was offered 18 months' additional work, but would not discuss what her duties would be.

The bank announced last Friday that Greenwald, who has held the presidency since its establishment in 1980, will go on a three-month sabbatical, starting Nov. 1.

Mitchell Rofsky, the executive vice president of the bank will assume the duties of president during that period.

The statement released last week said she had asked to be relieved of her daily duties and would spend the three months beginning Nov. 1 preparing a report of the role of consumer cooperatives and the NCCB in the American economy.

Greenwald has been a controversial figure at the bank. There has been a considerable turnover of employes -- reportedly including a number of firings. Attempts to form a union were not successful. And she was accused by smaller coops of slighting them after the bank's voting procedures were changed to favor larger coops and bank borrowers.

The director said a search committee would be formed to find a replacement for her. "What we need is someone with experience in a functioning bank, but without the image of a banker. How do you find such a person?" the director asked.

The director said the bank was operating in the black, but had been forced to write off a number of bad loans to cooperatives. "We want to survive as a bank, but it is difficult when the coops are struggling.

NCCB is now a private bank, chartered by the government. It funds nonprofit, consumer-owned organizations run by their members, which provide such services as food, housing, health care, furniture, day-care and auto repairs. These coops often have difficulty in borrowing from commercial banks. NCCB has over $120 million in government funds invested and a loan portfolio of $80 million.

NCCB has come under fire from some consumer organizations for not being more generous. It was also attacked by the Reagan administration, which sought to abolish it. Greenwald had a run-in with OMB director David Stockman, who threatened to shut off the bank's funds. She withdrew $60 million from the Treasury and put it in the bank's checking account.

Greenwald was in Rome yesterday and could not be reached for comment.