A method and an apparatus for cleaning a channel, especially a transmission and/or cooling channel, in any type of device, machine, installation, and/or tool, particularly in any type of heat exchanger and/or a molding core, cavity and/or insert is proposed, wherein a channel is cleaned through dynamic, bi-directional pulsation of cleaning medium inside the to-be-cleaned channel, the method being realized by a cleaning apparatus equipped with a diaphragm pump module, plugged either only in the feed side of the transmission line or in the feed side and in the return side, which, after connecting the diaphragm pump module to the external energy source and shutting off the flow control system from the reservoir and the feed pump, allows for putting cleaning medium into a state of two-way dynamic pulsating motion.