There are signs of reliability trouble coming out of the Mercedes camp.

On Saturday in Montreal, the brand new Mercedes engine fitted to Lance Stroll's Racing Point failed spectacularly.

The following day, before the Sebastian Vettel penalty controversy erupted, Lewis Hamilton's grand prix was almost spoiled by a pre-race problem.

He said afterwards: "I nearly didn't start the race because we had an engine problem.

"The guys really had their work cut out because to take the engine apart and rebuild it, it was very, very easy to make mistakes."

Auto Motor und Sport reports that the problem was with the hydraulic system. For three hours after the race, scrutineers had to check that the system had been replaced with an identical one due to strict 'parc ferme' rules.

And when Hamilton had tried to pull his newly-repaired Mercedes away for the warm-up lap, the anti-stall system was activated.

Renault reportedly asked the FIA whether the radio messages exchanged between Hamilton's car and his pitwall about the problem were legal.

"We thought the answer given to Hamilton fell under the technical directive," Renault's Alan Permane confirmed.

The FIA did not penalise Hamilton.