THE DAMAGE CONTROL squad seems to be taking over the transatlantic quarrel about compressors, turbines and the Siberian gas pipeline. The Reagan administration's policy hasn't changed, formally, but the tone is suddenly very different. The zealous and hectoring American rhetoric of the past couple of months has faded. American officials -- most recently the president's trade representative, William E. Brock, in London -- talk in terms of let's-see-what-can-be-worked-out. That's a change very much for the better.

The hard line on the pipeline was a product of the tense and disheveled period in June just before the president fired his secretary of state. A number of people who should have known better were competing to be more royal than the king. The president had been irritated by the Europeans at the Versailles meeting, and for a few weeks he was not getting the kind of solid advice that usually protects a president from the consequences of losing his temper.

Now that protective structure has been rebuilt. No one in the administration quite concedes that the original hard line was wrong. But there is in the air an acknowledgment that pursuing to the bitter end a blazing row with the Western European allies is not necessarily the most useful way to punish the Russians for repression in Poland.

Americans are having to come to terms with the political effects in Europe of the continued sales of American grain to the Russians. To enlist support for an embargo is exceedingly difficult under the best of circumstances. But when the Americans try to embargo shipments of European machinery, while merrily continuing to load wheat on Soviet ships, the European response is totally predictable. The Reagan administration has tried to argue that the pipeline will earn hard currency for the Soviets, while the grain sales cost them hard currency. The Europeans regard that as merely a smart debater's point, not serious politics. They know that the Soviets worry a lot more about their food supplies than about their monetary reserves.

In August, the administration saw that the pipeline policy wasn't working. The harder it pushed the Europeans, the harder they pushed back. Now it's September, and a cooler spirit seems to prevail. Last month's sanctions are being narrowed. It would serve American interests to find a discreet way to drop them altogether.