WHEN HELMUT KOHL arrives in Washington this week, the West German chancellor will be received dutifully rather than enthusiastically.

The administration was delighted when he replaced Helmut Schmidt in 1982 and his party won the national election in 1983. The Washington Post declared: "Germany returns to the reservation." The Social Democrats criticized American policy and spoke of Germany's national interests. Kohl depicted the Atlantic alliance as providential -- and evoked the American food packages of his youth.

He and his coalition partners, the Free Democrats, seemed ready to translate Reaganism into the German "Reaganismus." They were eloquent about the free market, and intent on cutting the fat from Germany's allegedly obese welfare state. Kolhl announced a "moral and spiritual renewal."

Our foreign policy managers interpreted this, correctly, as meaning water hoses and jail for Germany's youthful demonstrators and less access to the country's public television networks for anti-nuclear churchmen. Those old enough to remember the close U.S.-German ties under the late chancellor Konrad Adenauer saw Kohl as a modern heir to Adenauer.

Two years later, the German reservation teems with tribal revolt. Kohl's coalition has endured a series of losses in state and local elections, and faces more serious defeats in the spring. The Green Party, a coalition of environmentalists, anti-nuclear activists and miscellaneous social reformers, has displaced the Free Democrats as Germany's third party, and the Free Democrats face extinction. The coalition, then, may lose the next national elections in 1987.

Kohl's own bumbling amiability has not withstood the burdens of office. An harassed and irritable chancellor's political survival is very much in doubt. Openly in the German press, more discreetly in his party, more discreetly still among his erstwhile American friends, talk of his early replacement has begun.

Kohl's exit from office may be, indeed, as sudden as his accession to it. The corruption scandal threatening so many German politicians may yet result in his indictment. Details of the illegal funding of parties and persons by the billionaire Friedrich Flick have shaken Germany. The Social Democrats are tainted. The Greens have emerged as guardians of civic morality.

Kohl had to endure cross-examination before a parliamentary committee (and national television) by Otto Schilly, the Green Deputy who was the lawyer for a number of accused terrorists. Kohl admits to taking several hundred thousand marks in cash. It was illegal, he says, but everyone did it -- and the money went to his party.

Kohl describes himself as the victim of a plot to discredit the German state -- if not Western civilization. He has suggested that "foreign powers" may be resposible, and has accused the weekly magazine Der Spiegel, which broke the story, of "sewer journalism." Even those many Germans inclined to give constituted authority the benefit of the doubt find Kohl's defense absurd. Ordinary citizens and lots of Kohl's fellow Christian Democrats are outraged. The German left, meanwhile, is astonished. Its crudest depictions of capitalist politics now appear to be understatements.

Watergate overwhelmed a strong Nixon. The Flick scandal threatens an already faltering Kohl. His most conspicuous talent has been an iron refusal to make decisions. He has failed to dominate his cabinet or unify the coalition. From his redoubt in Bavaria, conservative leader Franz Josef Strauss -- ostensibly a Kohl ally -- has mounted open guerilla warfare against him.

Kohl's obdurate provincialism originally reassured many voters. His more sophisticated allies now question whether he understands the complexities of Germany's situation. Those complexities, to be sure, would bedevil any government and any leader.

Systematic economic drift has been the leitmotiv of the past two years. Social benefits for weaker groups have been cut. The coalition could not, however, attack the welfare state frontally: too many of its voters are attached to it.

The economy has turned up slightly, but many new investments buy machines that eliminate jobs. The nation's powerful unions are exceedingly combative. And as the coalition argues about environmental legislation, stolid burghers shocked by the destruction of their forests vote in droves for the Greens.

In foreign affairs, Kohl has presided unwillingly over a transformation of the terms of national debate. The deployment of American missiles has not ended the controversy over the alliance; it has enlarged it. It has become a discussion of the "German question."

Kohl has had the worst of both worlds. By extending credits to East Germany, he has evoked open West European and unspoken American disquiet about West Germany's fidelity. He also squandered his predecessors legacy of relatively good relations with the Soviet Union. He talked bravely of German reunification in Moscow, but did not say what political price West Germany would be willing to pay for it. He incautiously addressed a group which seeks the return of former Silesian German territory from Poland, encouraging the Soviet bloc to denouce West German "revanchism."

Within NATO, the Germans combine rhetorical protestations of loyalty with foot dragging on such issues as chemical weapons and military strategy. Finally, if Kohl's government has its own ideas on NATO's strategy or on East-West relations, they are very well-kept secrets. The chancellor's obvious lack of influence in Washington, meanwhile, serves the opposition as a convenient club with which to beat the government. It also diminishes West Germany's standing in both halves of Europe.

Kohl's most probable successor is the very effective minister of finance, Gerhard Stoltenberg. He was an historian and has had broad experience in both business and government. A Protestant conservative and an intellectual, he would demonstrate far more independence of the United States than Kohl. That is why, no doubt, some persons in the U.S. government prefer Lothar Spaeth, the governor of Baden- Wurttemberg. He is utterly untried in national and international affairs. Some experts and bureaucrats suggest he might be more pliable -- or at least more cooperative.

As Kohl's agony shows, German politics are made in Germany. The country isn't an American province. It will be less of one when, sooner rather than later, Kohl goes.