Abstract: A self-propelling harvester thresher has a drive motor, a cooler with a cooler fan for supplying a cooling air, a sieve device arranged before the cooler for retaining dirt particles entrained in the cooling air, an outer housing associated with the sieve device and having a smaller efficient surface than an air inlet surface of the sieve device. The housing has a side which faces toward the sieve device and is at least partially open. A conduit connects the housing with a suction side of a blower. A screening element is arranged inside the sieve device opposite to the open side of the housing. The screening element is formed as an inner housing having a surface which faces toward the end surface of the sieve device and has an opening. The opening of the inner housing of the screening element is greater than the opening of the outer housing connected with the blower.