Abstract: Heat exchanger cleaner for temporary installation in a heat exchanger or similar assembly to clean the heat exchange surfaces therein wth a jet of pressurized cleaning fluid. The cleaner has an arm temporarily pivotally attached to the inside wall of the housing of the heat exchanger assembly to support a spray head. The arm is free to swing in a radial plane adjacent one end of the core assembly. A drive, preferably having its working parts positioned outside the heat exchanger housing, swings the arm at a measured rate of speed to effect radial travel of the spray head across the exposed end of the core assembly. Circumferential coverage of the core assembly is provided by rotating the core assembly within the heat exchanger housing, employing the usual core assembly drive.The cleaner can be installed in a heat exchanger through an access opening in the housing adjacent one end of the core assembly. The swing arm of the cleaner drive can telescope to fit heat exchangers of varying diameter.