Worn or damaged belt: Lower or fluctuating boost indicates the belt has been exposed to oil or antifreeze. Replace belt.
Carbon build-up on bores and rotors: Carbon build-up can cause rotors to rub and drag down, indicated by lower or fluctuating boost levels. To alleviate this situation, select one of our Complete Supercharger Rebuild Services including a re-manufactured Rotor Assembly or Rotor-only Rebuild Services, both of which include rotor and case cleaning. Consider adding on the Optional High-Tech Rotor Coating during the Rotor Assembly rebuild. This is a common problem for Eaton M-Series superchargers that come on 1992 - 2002 GM products.
Leaking seal: Examine the outside of the snout for oil spots. Oil will sling off the back of the supercharger pulley when the seal is damaged and failing because of normal age and wear or excessive boost. Consider upgrading to a Premium Viton double-lip seal and Rotor Clip Snap-ring for a longer seal life. Our Premium Services & Products include this seal.
Bad bearings: Remove the supercharger belt and start the vehicle. The vehicle will run on the bypass valve without the supercharger. Is the noise in question is still there? If yes, then it is not coming from the supercharger. If the noise is eliminated by the belt-removal test, the supercharger bearings should be replaced immediately. The car can be driven without the supercharger belt because the bypass valve allows a reduced air stream through to the cylinders. If the supercharger is damaged, temporary deletion of the supercharger will reduce further damage to the supercharger until it can be rebuilt.
Scuffing of the Rotors or the End Plate: This indicates a worn bearing. The ball bearings in the front bearing plate are the only bearings controlling back and forth movement. When the supercharger is new, it starts with a .003 backlash in the rotors. So when they wear a little and have a .007 backlash, the rotors start to scuff the back of the front bearing plate. Replace with re-manufactured Rotor Assembly.
Coating Peeling or Chipping Off: As the bearings wear, they start to allow a back and forth movement in the rotors. This changes the timing of the rotors, allowing the flutes to scuff and damage each other. Replace with a re-manufactured Rotor Assembly. If allowed to go on for too long, this linear movement ruins the rotors beyond economical repair.
Worn Coupler (a.k.a. Universal): Supercharger rattles. To test, remove belt and move the supercharger pulley back and forth by hand. If it has backlash, replace coupler.
Diagnostic Information for Eaton Rotor Assembly Rebuild Service
Scratches on the outer edge of rotors: How can you tell the rotor rear needle bearings need to be replaced? Look for scratched ends on the rotors. When the rear needle bearings need to be replaced, the outer edge of the rotor will have scratches from contacting the case. This happens because the rear needle bearings are allowing too much rotor radial movement. The needle bearings only control radial movement.
Scratched Rotor Bearing Plate: How can you tell the ball bearings in the rotor bearing plate need to be replaced? Look for a scratched rotor bearing plate. The bearings in the rotor bearing plate need to be replaced when the rotors are putting scratches in the rotor bearing plate’s sealing surface.
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Eaton Supercharger Diagnostic Information