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.
“And that's not something I can have an influence on. So all I can do is stay focused and stay close to the team, try to help them find the next improvement.
“It's part of racing. It's been part of it from day one. So these things happen. And, yeah, I'm more focused on trying to move forward in terms of performance and find our way back into top 10.”
He added: “I couldn't finish qualifying and couldn't finish the race. So, obviously not my weekend.
"I’ve got to just stay focused, try to look for that next step of improvement. I think we are fighting a little bit too hard right now to get into the top 10.”
Asked about the Haas failure after the race Ferrari boss Fred Vasseur said it was “too early” to come to any conclusions.
Hulkenberg eventually finished the Silverstone event in a lowly 13th place, after early contact with Sergio Perez saw him lose his left front wing endplate. That triggered a premature stop which put him out of sequence.
“Not great, boring,” the German said of his afternoon. “Because obviously the early pitstop, the early damage to the front wing was costly, and put us out of the race, basically.
“And then we needed the safety car, but it happened kind of too late at the end of the race. Then I think the pace after that and traffic was actually decent, but there was just a DRS train, and it was difficult to make any or much progress.”
Regarding the clash with Perez, he said: “It's just unfortunate. Actually, I didn't even feel it. But we must have touched [on the] exit of four.
“I think it was a little bit impatient from him because he had DRS after Turn Six anyway, he would have gone easily by me. It was a little bit rushed and unnecessary, I thought. But yeah, it is what it is now.”
Additional reporting by Jake Boxall-Legge
