"New GP, new problems," Mercedes chairman Niki Lauda told Osterreich newspaper.
He also told German broadcaster RTL: "Malaysia will be more difficult (than Melbourne).
"In Sepang actually we are starting from scratch because of the high humidity and temperature -- I doubt it will be below 35C.
"In such circumstances, effective cooling of the power unit would indeed be a problem. We will have to make changes to the car to resolve the issue."
Lauda's Mercedes colleague Toto Wolff agrees: "I think all the teams are seeking to create the most efficient cooling system.
"Every test or race weekend has been more difficult than we expected, so it will be difficult to cope with the heat in Malaysia," he admitted.