Abstract: A hermetically sealed compressor has a supply of lubricant contained in its sump defined by the inner surface of the hermetically sealed shell. The level of the lubricant supply is above the bottom wall of the compressor cylinder block. The cylinder block includes a drain opening in the bottom wall thereof. A valve is biased to close the drain opening to prevent oil from flowing from the sump into the cylinder block as a result of the pressure in the block being lower than the pressure within the shell acting on the surface of the oil in the sump when the pressure in the cylinder block is greater than the pressure within the shell. The valve permits the drainage of lubricant from the cylinder block to the sump.