F1 testing: McLaren-Honda suffers failure with new MGU-K seal

It is now working on a new and "re-engineered" solution for Sunday.

The team first had to abandon running on Thursday due to the issue and then ran a limited programme on Friday while waiting for a redesigned seal.

This was fitted for Saturday, but the problem returned even with the revised part, forcing McLaren to spend much of the day in the garage before eventually rejoining to run with reduced power.

On Friday, Honda chief Yasuhisa Arai had shrugged the initial seal problem off as an isolated "quality issue" that would be resolved by the new part.

A McLaren statement said: "After the morning session, the car fed back MGU-K issues similar to what we experienced on Thursday, so we brought it back to the garage.

"After a thorough check, we have decided to resume testing with limited power to the MGU-K.

"A new and re-engineered seal is scheduled to arrive and will be applied later this evening."

Despite running with an engine that Arai admitted "had some risks" due to the Thursday seal problem, McLaren had its most encouraging day so far on Friday and completed 59 laps with Fernando Alonso.

The revised seal had arrived during Friday's running, but McLaren opted to stay on track with the Thursday engine-spec rather than losing running time to change the power unit, in the hope that it could do so overnight and have a smooth Saturday.

Alonso is due to take over from Jenson Button again on Sunday.