Confirmation from AMuS that Mercedes did in fact have a cooling problem, and that the solution has finally arrived for Barcelona . . .
Excerpt:
"We checked the ten teams for news on Thursday. As usual, most of the news in Barcelona was on the technical front. Thursday is the PR day before a Grand Prix. auto motor und sport will be looking for stories and rumours in the paddock for you. We ask the engineers what's new about the car and the drivers what they think of the race. Here is our tour through the ten garages.
Mercedes has completely rebuilt his car once again. The changes are almost as extensive as between the first and second week of testing in winter. The following components are new or modified: Front wing, rear wing, side boxes, baffles, underbody front and rear, rear view mirrors,
cooling of the drive unit."
https://www.auto-motor-und-sport.de/for ... barcelona/