Russell was instructed to stop at Turn 1 after completing his final Q3 lap, with his stranded Mercedes triggering a yellow flag during the closing seconds of the session.
Mercedes initially identified a loss of water pressure before further inspections confirmed the internal combustion engine needed to be replaced ahead of Sunday’s race.
The team will fit Russell’s fourth ICE of the 2026 season, keeping him within the permitted allocation and allowing him to avoid a grid penalty.
“During George’s final lap in Q3, we detected a loss of water pressure on his car and instructed him to stop as a precaution once he had completed the lap,” a Mercedes spokesperson said.
“Following further inspection, we have elected to change his power unit ahead of tomorrow’s race, moving to his fourth unit of the season and thus within his season allocation.
“As the change is also being made to replace a damaged component with one of the same specification, George will incur no grid penalty.”
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Russell’s fourth engine is the final one he can use without automatically receiving a grid penalty, placing him on the same number of units as teammate Kimi Antonelli.
The failure is believed to have been triggered when Russell struck the kerbs at the exit of Turn 4 during his final attempt, with the vibrations causing the leak inside his power unit.
Russell said the issue sent water onto his rear tyres and contributed to a sudden drop in temperature, ruining a lap which had initially felt promising.
“We had a water leak, hit a bump in Turn 4,” Russell explained.
“The lap was feeling good until then and then suddenly the lap wasn’t. I didn’t think much of it, and the team told me the water was spraying over my tyres.
Verstappen spinning, Russell stopping on track, Lewis parking at the P1 board!
It was a chaotic end to qualifying 😮#F1 #HungarianGP pic.twitter.com/tD2JTERvr4
— Formula 1 (@F1) July 25, 2026
“As soon as we saw it in the data, the water leak, suddenly my tyre temperatures got really cold on the rear.
“So, I don’t think much more, top three definitely not possible, but maybe a few positions higher would have been there.”
Russell later likened the problem to having water sprayed directly at his tyres as he attempted to complete the lap.
“It didn’t really affect anything, although there was a water leak and we saw on the tyre temperatures that water was spraying on the tyres during my last lap, so my last lap was rubbish,” he said.
“I think there’s maybe a reason for it because it was like a water pistol being sprayed at the tyres, which doesn’t necessarily give you more grip.”
Mercedes team principal Toto Wolff confirmed the engine had been damaged after Russell rode over the kerb.
“George was unlucky with what looked like a water leak, so it was an underwhelming session,” Wolff said.
“It’s a water leak that appeared when he was riding over a kerb.”
Russell had already struggled to challenge at the front before the technical problem, with Mercedes unable to reproduce the form which had secured every pole position during the opening part of the season.
Lando Norris ended that run by taking pole for McLaren, while Antonelli qualified fourth and Russell finished seventh.
Russell will start ahead of his teammate, however, with Antonelli later awarded a three-place grid penalty for failing to slow under yellow flags.
Russell believed Mercedes’ difficulties were linked to its inability to generate sufficient tyre temperature over a single lap, although the characteristics could prove more favourable during the race.
“The truth is that this whole weekend, we haven’t really had the pace,” he said.
“We’ve looked very strong in the race pace. Did we strike the right balance between the Quali set-up and the race set-up is maybe the question we’ll have answered tomorrow. Just struggled to get the tyres switched on all day.”
The Briton pointed to Mercedes’ long-run performance on Friday as evidence that the team could still be more competitive across the grand prix distance.
“Yesterday we were a second off in Qualifying practice but in the race pace we were the quickest, which tends to say you’re not getting enough temperature in the tyres for that Qualifying lap,” Russell said.
“But then in the race when you want to keep the tyres cooler, that’s where it pays off. This is a track where it’s very difficult to overtake so as I said, perhaps we haven’t struck the right balance.
Maybe tomorrow when we’ve got good pace, fingers crossed, we’ll say we have.”
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