Fernando Alonso was forced to cut short his run on the penultimate day of Formula One's pre-season testing in Jerez after his McLaren encountered engine problems.
The F1 constructor announced a link with supplier Honda ahead of the 2015 season, but the opening days of testing have seen the team struggle with reliability issues.
After the first two days Alonso, who announced his decision to leave Ferrari for a second spell at McLaren at the end of last season, and team-mate Jenson Button had managed to complete just six laps each.
The Spaniard enjoyed a more productive session on Tuesday, managing 32 laps before he was forced to call it a day.
"We've had a loss of cooling water pressure and have removed the power unit for inspection," read a Tweet from McLaren. "That's a long process, so it ends today's running.
"We can replace those components ahead of running tomorrow.
"The issue was promptly spotted by Fernando on an out-lap - so quick to trace."