Austrian Grand Prix: Overheating problems end Mercedes' winning streak
Mercedes Formula 1 boss Toto Wolff says his team have to fix the overheating problems that stopped them fighting for victory in the Austrian Grand Prix.
Valtteri Bottas and Lewis Hamilton finished third and fifth respectively after the issue forced them to drive slowly in the race.
"We knew it was our Achilles' heel and we are carrying the problem since the beginning of the season," Wolff said.
"It was painful to watch, cruising, not being able to defend or attack."
The result ends Mercedes' eight-race winning streak at the start of the 2019 season, a sequence which has seen Hamilton establish a commanding 31-point advantage at the top of the drivers' standings.
- Verstappen keeps win after investigation
- Hard racing or unfair? Verstappen highlights F1's dilemma
- Austrian Grand Prix race results
- Chequered Flag podcast: What is fair racing?
The lack of cooling on the car in Austria meant that Mercedes had to run the engine below its maximum race power capability and the drivers had to back off long before the corners using a method called "lift and coast".
The team opened up all the possible cooling ducts but Wolff said the car was "right on the limit. We couldn't do anything any more. There was no step left".
The problem was caused by the high ambient temperatures in Austria - the race started in 33C air temperature and 58C on the track. The 700m altitude at the track - which means there is less air to cool the car - exacerbated the problem.
Wolff added that he was concerned about the potential for problems at other hot races this summer.
"We will react," he said. "There is no other option.
"I am really hoping for the typical English weather in Silverstone [the next race] so we can gain a little bit of time to sort our problems out.
"But then there is no question, there is no alternative but to fix our problems for the coming hot European races, Hockenheim and Budapest."
Wolff said he believed Hamilton could have fought for the win regardless had he not damaged the front wing over kerbs in his first stint, requiring it to be changed at his pit stop.
"When you look at the positives, we had the car pace, we were running the engine turned way down, lifting and coasting for up to 400 metres. Almost having no throttle rolling downwards and still putting in decent lap times," he said.
"So I think we would have a chance to fight for the win. But we were limited by the cooling problems."
But Hamilton said he did not believe that was the case.
"No way," he said. "We were lift and coasting 400 metres-plus a lap. If we didn't have to do that we would have pace, I think, but unfortunately that was the way it was. I could never get close to anybody."