Jenson Button and McLaren-Honda suffered another frustrating day in Barcelona on Saturday when their MGU-K engine seal design failed again.
The team was forced to abandon running on Thursday because of the same problem and that compromised their performance on Friday, although Fernando Alonso was still able to manage a significant run-out.
The issue was meant to be resolved for the third of the four days of testing but there was another failure and the team is now in damage limitation mode before Sunday’s final day, when Honda is to “re-engineer” the faulty part again.
Button, the slowest driver on show, was able to run only 24 laps, and many of them were on reduced power.
The British driver, who will be replaced by Alonso on Sunday, was also involved in a red flag incident near the end of the day when he and Max Verstappen (Toro Rosso) both parked in the pit exit.
On Friday Alonso warned that McLaren may not be ready for the first race in Melbourne on 15 March after a series of reliability issues.
For the second time in three days the fast time on Saturday was set by the Lotus of Pastor Maldonado, who was running on super-soft tyres.
Second quickest was Verstappen, who put in more laps (129) than any other driver. In terms of pace, Verstappen was followed by Lewis Hamilton (Mercedes), Marcus Ericsson (Sauber), Sebastian Vettel (Ferrari) and Daniil Kvyat (Red Bull).
The day started badly for Vettel, who spun on to gravel on his out-lap as he struggled to come to terms with his cold tyres. But he went on to complete 105 laps.
