Valtteri Bottas is forced to sit out the early part of FP3 as Mercedes scramble to prep his W08 for the hour-long session.
Mercedes brought an updated power unit to Barcelona, with improved reliability but Bottas has now reverted to the previous engine after a water leak was discovered this morning on his new unit.
Last night however, Mercedes had discovered an electrical issue with the Finn's new unit, forcing the team to use up the first of its curfew jokers.
It was while putting the engine back together that the water leak was detected. Mercedes then decided to re-fit the power unit which Bottas had used in the first four races of the season.
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GALLERY: All the action from Barcelona on Friday
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