Although Americans are going into debt for housing at record high levels, they are making their monthly mortgage payments more faithfully than at virtually any time in the past quarter century.

New data compiled in a nationwide survey by the U.S. League of Savings Associations indicates that mortgage delinquencies hit the lowest rate for the month of March since the organization began monitoring consumer repayment patterns in 1953.

In a poll of more than 1,000 S&Ls-representing over half of all S&L assets in the country-the league found that only .73 percent of outstanding mortgages were delinquent, or unpaid for 60 days. This was down from .95 percent registered in March 1977, and far below the levels that prevailed during the 1950s and 1960s, when rates nearly twice as high were recorded.

Metropolitan Washington delinquencey rates on mortgage loans are even lower than the national figures. The executive vice president of the area's largest S&L, Robert McConkey of Perpetual Federal, says his institution's annual rate is between .5 and .6 percent-a level industry sources confirm is typical for Washington overall.

Rates in economically weaker sections of the U.S., on the other hand, such as selected urban markets in New England and New York's Long Island, tend to be two or three times the national average.

Delinquencies for mortgages are considered an importance economic and social indicator of how well consumers are handling their debt burdens.

When the housing market experiences a surge of buyer interest and huge net additions to mortgage debt-like the over $100 billion during 1978-the danger exists that some consumers will overextend themselves. This possibility has been worrisome recently to economists who point to households" mounting mortgage and personal debt as the harbinger of waves of delinquencies and forclosures.

Behavior patterns among American homeowners, however, have been going in the opposite direction for more than 18 months, a significant but little-publicized fact. No formal studies have been done to determine why this pattern is energing, but contributing factors may include the following:

Families now view residential real estate as their one solid hedge against inflation, their one reliable bank account. They are intent on preserving their investment from even the remotest chance of forclosure, whatever the financial sacrifice. If bills have to be delayed because of a financial crunch, those bills are less likely to be the mortgage. In earlier decades, by comparison, families were more conservative about incurring mortgage debt, but more willing statistically to delay payments to their mortgage lender.

Consumers today may be somewhat better managers of their own debt burdens, more sophisticated about handling their families' cash flows. They may feel constantly strapped to make ends meet, but steadily rising incomes enable them to avoid defaults on fixed-payment mortgage debts.

The market shares of low-down payment, government-backed FHA and VA mortgages have declined sharply since the 1950s. Their traditionally higher delinquency ratios may therefore be exerting a smaller impact on national averages.

None of this is to suggest, of course, that current low U.S. mortgage delinquency rates would withstand a serious economic recession. When homeowners lose their jobs because of industry downturns-however passionately they may be attached to their property as an inflation hedge-they stop paying the mortgages on them.