A back pressure chamber seal for use in a scroll type compressor that is located between the adjacent surface on the back of the orbiting scroll and the machine casing. Seals are loosely received in endless grooves formed in one of the two adjacent surfaces and are magnetically held in contact against the other adjacent surface and one wall of the groove to provide a sealed region. A pressurized fluid is delivered into the sealed region to provide an axially disposed biasing force acting against the orbiting scroll.