In the high temperatures at Sakhir the team discovered that it had insufficient cooling to its front brakes, which restricted any long runs.
New parts were flown in for Saturday, which improved the situation. However, they were only a temporary fix, and the team is working towards a definitive solution for next weekend’s Bahrain GP.
With Daniel Ricciardo sidelined by COVID-19, Lando Norris had the MCL36 to himself, and over the three days the Englishman completed 50, 60 and 90 laps.
That left the team with a much lower overall total than it had planned, and thus a lot of routine work was not completed.
"The test definitely didn't go to plan,” Seidl said in an interview with F1 TV. “We had an unexpected problem on the front axle with the brakes, which limited our running quite a bit. Especially when it came to long runs.
“So it puts us definitely a bit on the back foot. Still, I think there was still a lot of positive runs we could do as well, we still could work on the car to extract more performance from it. We still could bring further upgrades to the car as well. So that was positive.
“But definitely we have this issue. And we simply are up against the time in order to bring upgrades to the car to solve the issue, which we could do to a certain degree, but not to the full extent.
“And now simply hope that with the upgrades we get for next week that the problem is finally solved, and we can try to come back."
Seidl conceded that the new parts didn’t completely solve the problem.
"We made steps,” he said. “But due to the time constraints we have we could only do limited changes, also with the great support we had from home.
“So it allowed us to actually to do some longer runs again, today in the morning, trying to get some further ones in today in the afternoon. But let's say the real solution will only be available for next week.
"In the end with the track layout here, with the high temperatures, just not enough, what we had, and also not enough in terms of time to get the new parts here to the track. That's why we simply have to wait now for next week.
“But I'm very confident that we can solve that issue. And then speak more about performance again."
Seidl insisted that the track running that Norris and the team did manage to achieve had been productive.
"We left Barcelona after a really positive test. I think also what we have seen here so far from the car, when we did the runs we could do, I think we definitely have a very healthy platform going into this new era of F1.
“But of course, unfortunately, we missed to tick a lot of boxes now in these three days, because of the limited running we could do. So definitely not fully happy."
Seidl said it was hard to judge McLaren's form relative to rivals, although most observers suggest that it currently has the third or fourth best package.
"In terms of pecking order I think it's still too early or too difficult to say really where everyone is.
“Some cars look really strong, since Barcelona already, like the red Ferrari, some other teams as well. So the main thing at the moment is to just focus on ourselves and get this problem sorted, and then see where we are next week.
“I'm sure Mercedes knows exactly what they're doing. And they will be there next week, no doubt. Again, it's difficult to say where we really are.
"Until next week, during the race weekend, we will not know where everyone is."
