McLaren F1 racing director has admitted that the team hadn't expected to find the new MCL32 so glitch-prone on the first day of pre-season testing at the Circuit de Barcelona-Catalunya on Monday.
Fernando Alonso was barely able to complete an installation lap in the morning before having to crawl back down pit lane with an engine problem that the team later ascribed to an oil leak which led to an engine change over lunch.
"We have an oil system problem," Boullier explained. "That's all that we know now. Honda are investigating what is going on and I guess they will tell us what happened."
When the car went out in the afternoon it once again suffered problems on its installation lap and barely made it back to the garage. The reliability problems had come out of the blue for the team, according to Boullier.
"It's disappointing because yesterday we had a filming day, we did 100km, and more or less everything went right, so this morning it came as a little bit of a surprise to have a problem.
"Honda's engine was running in a safe mode [on Sunday] so there wasn't much to compare. We could see a difference in high speed corners, for example, that the car was much faster, but you can't investigate much."
Once the car was checked over, Alonso did go on to complete 29 laps in the afternoon and finished with a personal best time of 1:24.852s for the day.
With Alonso losing so much running time on Monday, and Stoffel Vandoorne due to takeover behind the wheel on Tuesday, Boullier admitted that the week's test schedule might have to be tweaked.
"We may obviously reconsider the schedule," said Boullier. "Alonso knows minute-after-minute what is going on.
"He was not very happy this morning, but he was here yesterday as well, he drove the car yesterday for a few laps and got a feel of the car."
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