The Senate voted 56 to 38 yesterday for a two-year extension of automobile-pollution cleanup deadlines instead of the four-year stretchout favored by the auto industry.

In a second key test on the clean-air bill the Senate voted 61 to 33 to kill an amendment weakening proposed air-pollution controls for national parks and other clean-air sections of the nation.

The amendment, similar to one passed by the House, would have allowed new factories and power plants to exceed the proposed standards for 18 days a year, though only up to specified levels that wouldn't endanger public health.

Defeat of this amendment was assured when the influential Sen. Henry M. Jackson (D-Wash.), chairman of the Senate Energy Committee, who had previously told sponsors he might back it, informed them he would not do so.

Both votes were a victory for the Carter administration, the bill's sponsor. Edmund S. Muskie (D-Maine) and a coalition of environmental and local government organizations which opposed loosening standards in the bill.

The victory on auto deadlines was engineered by Minority Leader Howard H. Baker Jr. (R-Tenn.). In place of the 1978 cleanup deadline in current law, the auto industry and the United Automobile Workers wanted a stretchout to 1982. The Public Works Committee recommended a stretchout only to 1980. The industry amendment granting a 1982 deadline was sponsored by Sens. Donald W. Reigle Jr. (D-Mich.) and Robert P. Griffin (R. Mich.) and appeared to have substantial strength.

Baker offered a compromise retaining the committee's 1980 deadline but somewhat softening some of the committee's intermediate requirements for 1979. Muskie and the administration, fearing the Riegle amendment would win, united behind the Baker proposal and it carried. The House, by contrast, has voted for 1982.

While senators were debating the Riegle-Griffin substitute on the floor, former UAW President Leonard Woodcock (now U.S ambassador-designate to the Peoples Republic of China), present UAW President Douglas Fraser and Chrysler President John Richcardo were busy in the public lobby of the Senate seeking support for the amendment. Only a few feet away spokesmen for the Clean Air Coalition and other organizations were buttonholding senators on the other side of the issue. President Carter opposes the Riegle-Griffin amendment.

Riegle and Griffin argued that forcing the industry to meet the stadards by 1980, instead of letting them ease into technically better tailpipe-emissions controls two years later, would means a loss of 134,000 barrels a day of oil over the next six years, added costs to consumers for the cars, with comparatively very little added reducation of tailpipe pollutants to show for expense.

But Muskie and te administration said sticking to a 1980 deadline would force the indstry to use a higher technology sooner, such as the three-way catalytic muffler, diesel engines, the Honda-type stratified-charge engine and alternative engines a few years down the road, which would simultaneously be cleaner and use less fuel.

During the debate both on the national park amendment and the auto deadlines, Muskie kept pounding at the theme that, according to a 1974 National Academy of Sciences study, 15,000 persons a year die from air pollution, of whom 4,000 are victims of auto pollution.

The fight over proposed controls for national parks, wildernesses and other clean-air sections of the nation was a repeat of one on last year's clean-air bill, which ultimately died on the last day of the session.

The Musike bill provides that in areas of the country which already have clean air, or which are far cleaner than the minimum standards required for public health and welfare, additional industrial plants and powerplants shall not be built if they will cause "significant deterioration" of the quality of the air. These areas are the open, undeveloped sections of the nation.

It then specifies that new powerplants, industrial plants, cement plants and so forth are forbidden in the areas if they put more than a certain (rather small) amount of new sulfur dioxide or particulate matter into the air.