It came after two earlier failures for Hulkenberg himself, which have added to the team’s woes as it fights to develop a car which is quick in qualifying but is usually too hard on its tyres in races.
Magnussen had stopped on track in Q1 at Silverstone after suffering an oil pressure issue, although it was believed at the time that the PU - which was new in Austria - had not been damaged and could still be used.
However an older, high-mileage unit was fitted for the race, and that’s the one that failed.
In the race, he was forced to pull over and park the car on lap 32 after a sudden loss of power.
Asked if the failure on his team-mate's car is a concern, Hulkenberg said: “I think so. I mean, I had a couple this year too, it definitely something where the alarm bells are ringing and it seems to happen more just on our team and car.
"So I think definitely take it seriously and we need to investigate and find out why.”
Haas has endured a series of reliability issues this season and Magnussen says he is trying not to get overly frustrated by the problems.
“It's one of those things that is much out of my control that I don't tend to worry about it,” said the Dane. “Of course, I offer my feedback if they need it, but it's really up to them to run the engine.
Source: Autosport