Abstract: An apparatus for cleaning hydraulic fluid residue from a system such as an automatic transmission cooling system of a vehicle includes a solvent dispensing reservoir, a solvent recovery reservoir, and a pneumatically controlled check valve coupling the solvent dispensing reservoir and solvent recovery reservoir. The check valve responds to pneumatic pressure to block flow from the solvent recovery reservoir into the solvent dispensing reservoir and to pressurize the solvent reservoir to propel solvent into the system to be cleaned. In the absence of pneumatic pressure, recycled solvent in the solvent recovery reservoir can flow into the solvent dispensing reservoir for reuse. The apparatus is preferably for cleaning automotive automatic transmission cooling systems of accumulated "varnish" and other debris.