McLaren-Honda F1 test programme compromised until Saturday

Button completed 21 laps during the opening morning of the Barcelona F1 test on Thursday, holding sixth in the standings heading towards lunchtime, but then had to park in the McLaren garage due to a faulty seal.

Honda said the engine would have to be changed and that until the relevant component was redesigned there was no guarantee that the problem would not re-occur.

That means McLaren's running on Friday could also be compromised, so the team will now put Fernando Alonso in the car to prevent Button from having both of his days affected

Honda's R&D chief Yasuhisa Arai said: "We had to stop running this morning after discovering a faulty seal on the MGU-K.

"That faulty part then caused an issue that requires full replacement of the power-unit - and the time needed to make those changes effectively ends today's programme.

"We'll need to run a redesigned component to avoid a potential repeat of the problem.

"Unfortunately, we won't be in possession of that updated part until Saturday, which means that we may face the same problem when we run again tomorrow."

Arai said Honda and McLaren would still do all they could to make good use of Friday despite the potential for another failure.

"Such issues are all part of testing, but we'll make the best changes we can overnight, and will plan for a productive day of running - with Fernando behind the wheel - tomorrow," he said.

"Hopefully, with a bespoke solution ready for Saturday, both drivers will have an opportunity to get some useful laps under their belts, with Jenson driving on Saturday, and Fernando concluding the test on Sunday."