Montreal, June 9: Mercedes faced a late rush to get Lewis Hamilton's car ready for the Canadian Grand Prix after discovering a hydraulic leak on Saturday.
Hamilton and team-mate Valtteri Bottas are running with a first engine upgrade of the season at the Circuit Gilles Villeneuve this weekend.
Ferrari's Sebastian Vettel secured pole for the first time this year in Montreal, with Hamilton second on the grid and Bottas starting Sunday's race back in sixth.
Silver Arrows boss Toto Wolff expressed his concern after Racing Point's Lance Stroll saw his new power unit burst into flames during FP3.
Mercedes revealed a couple of hours before the race was scheduled to begin that a fault had been detected on Hamilton's car.
"We discovered a hydraulic leak on Lewis' car late yesterday afternoon," read a tweet from the manufacturer on Sunday.
"We have diagnosed the source and are now putting the car back together ready for the race."
Hamilton holds a 17-point lead over Bottas in a season that Mercedes have dominated so far.