McLaren's running in the first 2018 Formula 1 test at Barcelona was compromised by a "£2 problem" earlier this week.
The MCL33 suffered some fire damage on Tuesday when the bolt failed and the exhaust came loose while Stoffel Vandoorne was driving, leading to a lengthy period of downtime.
On Thursday McLaren had a different issue with high temperatures at the rear damaging the bodywork due to a hole in a heat shield, although it was cosmetic and not much time was lost.
The car has continued to run with the same burn-damaged engine cover, due to a lack of a replacement.
"It's a stupid bolt that broke in the exhaust," said racing director Eric Boullier of the first issue.
"So it was a £2 problem which cost us a lot of track time, because everything was burned after in the back of the car, so we had to rebuild the gearbox and the back end.
"Nothing else than this. It didn't cost us much to revise the design, it's more about the track time we lost. As you can see the design is still the same and the car is still running."
Regarding Thursday's problem, he added: "Cooling is the first matter that every team is managing in the first week of testing.
"In a case where you have a new engine partner, you might have some sort of heat soak pocket in the car.
"We can see on the bodywork there are a couple of stripes, but this is just because we have to make sure there are some proper heat shields in place, consider all the heat soak pockets, and make sure we can modify and change the cooling inside the bodywork."
Despite the problem, better weather allowed McLaren to make some good progress with the car on Thursday.
"Finally we got rid of bad weather and mechanical glitches in the car so we could follow our programme," Boullier added.
"We obviously adjusted our programme, we have compressed it to give some priorities to some items, but today we are now starting to gather data on aero, and even work on some mechanical changes now."
McLaren has done a lot of running on Pirelli's new hypersoft tyre, even though it will only be used at a small number of grands prix.
"It's just because tyre models predicted that if it's too cold this is the only tyre that you can work with," Boullier explained.
"It turned out that everybody tried soft or ultrasoft or hypersoft or whatever it is, the one that also worked very well is the medium tyre."
Boullier says the team has clear targets for next week's second test.
"First to do a race distance, and obviously doing also some live pitstops, which obviously we've given more focus this year, so we have some new equipment and stuff to try," he said.
"So a race distance will be the key next week."
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