How to handle unauthorized requests(status with 401 or 403) with new httpClient in angular 4.3

You should use your interceptor and just handle it like this:

@Injectable()
export class AuthInterceptor implements HttpInterceptor {
    constructor(private router: Router) { }

    private handleAuthError(err: HttpErrorResponse): Observable<any> {
        //handle your auth error or rethrow
        if (err.status === 401 || err.status === 403) {
            //navigate /delete cookies or whatever
            this.router.navigateByUrl(`/login`);
            // if you've caught / handled the error, you don't want to rethrow it unless you also want downstream consumers to have to handle it as well.
            return of(err.message); // or EMPTY may be appropriate here
        }
        return throwError(err);
    }

    intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    // Clone the request to add the new header.
        const authReq = req.clone({headers: req.headers.set(Cookie.tokenKey, Cookie.getToken())});
        // catch the error, make specific functions for catching specific errors and you can chain through them with more catch operators
        return next.handle(authReq).pipe(catchError(x=> this.handleAuthError(x))); //here use an arrow function, otherwise you may get "Cannot read property 'navigate' of undefined" on angular 4.4.2/net core 2/webpack 2.70
    }
}

no need for the http service wrapper.

to use the router you’ll need a factory provider like:

 providers: [
     {
         provide: HTTP_INTERCEPTORS,
         useFactory: function(router: Router) {
           return new AuthInterceptor(router);
         },
         multi: true,
         deps: [Router]
      },
      .... other providers ...
  ]

where ever you’re providing the interceptor (probably app.module). don’t use an arrow function. they aren’t supported in factory functions when you try to build for prod.

Working plunk: https://plnkr.co/edit/UxOEqhEHX1tCDVPDy488?p=preview