Before qualifying, Nico Rosberg had to revert to an older engine, when a problem with his new specification unit was discovered.
Mercedes went into the weekend with concerns about the new spec, which will set the direction for development ahead of 2016.
“Because there are no more tests in the year, we have to test in the race,” boss Toto Wolff had warned. “We cannot expect an entirely trouble-free weekend.”
So there were worries that the Rosberg problem could also strike the unit being used by Hamilton, who powered to pole with it on Saturday.
That could have meant a pre-race engine change and therefore grid penalty for the championship leader.
But after an investigation overnight, Mercedes is no longer worried about Hamilton’s power unit.
That is because the problem with Rosberg’s engine was “traced to a leak in the cooling system”, Mercedes announced. The issue was therefore “not a problem with the engine itself”.
“The (Rosberg) power unit will be inspected in the coming days to decide if it can be used again at future races,” the team added. (GMM)