Haas fielded two very unhappy race drivers in practice ahead of the Spanish Grand Prix.
Romain Grosjean, for one, swore on the radio about an "undriveable" car.
"Romain wants us to make progress," boss Gunther Steiner is quoted as saying by Auto Motor und Sport.
"If he tells us only what we want to hear, we will not do that."
Also furious in his post-Friday media rounds was teammate Esteban Gutierrez, who has had a much poorer run of car reliability than Grosjean so far in 2016.
"I do damn good work but those on the outside can't see it," he is quoted as saying by Speed Week.
"I have been fast in every race car, why should that no longer be the case? My job is to drive, the job of the team is to solve the problems of the car."
Steiner said that Gutierrez has the right to be upset.
"I, too, would be upset, because when he is on the track, we can see that he has the speed," said the American team's chief.
Grosjean and Gutierrez qualified 14th and 16th respectively for today's race.
