McLaren racing director Eric Boullier says his Formula 1 team has no obvious explanation as to why Kevin Magnussen suffered heat issues in the cockpit during the Singapore Grand Prix.
Magnussen battled through the pain barrier to 10th place at the Marina Bay circuit, and had to be attended to by a doctor afterwards.
With no indication of what caused the problem coming to light on telemetry, the team has begun an investigation into what happened in the car, and especially why the water in his drinks bottle overheated.
"One big problem was the [drinking] water was boiling - it was boiling in his mouth every time he was drinking," explained Boullier.
"It was strange, I don't know why - they are investigating what was wrong because everything on the telemetry, like batteries, was normal."
Although Magnussen downplayed his situation afterwards with a stoical tweet, Boullier had nothing but praise for the way the Dane kept going.
When asked by AUTOSPORT if it was an heroic performance to finish in the points with all that he was going through, Boullier said: "It was. He was okay when he got out of the car, but you could feel that he gave it his all."
FIRST LAP DRAMAS NO WORRIES
Although Magnussen was praised for the way his race ended, Boullier admitted that there had been a little bit of frustration about his scrappy first lap - when he ran wide in his desperation to defend from team-mate Jenson Button.
"You don't like to see your cars off track, I think," he said. "And I don't want to protect him, but the rain last night also made the track a bit green.
"He was probably caught by surprise by the grip difference between qualifying and the race."
Boullier said McLaren was also waiting for information from Mercedes as to the cause of team-mate Jenson Button's car stopping when he was running in the points.
"It was a power box issue, and we are now waiting for the information from Mercedes as we have no access to this data."