When I start my engine the vacuum gauge reads zero vacuum, but as the engine RPM increases, the gauge will indicate vacuum. What causes this?
The carbon vanes inside the pump are sticking in rotor slots. Oil or solvent has entered the pump either from a bad oil seal in the engine case at the pump mounting area, or from pressure washing the engine with an oil-based solvent (spraying directly on the pump). The oil or solvent will work its way up into the pump through the drive end, mixing with graphite dust and turning into a paste like material. A Dry Air Pump is just that: DRY. As the carbon rotor and vanes wear, they produce graphite dust which lubricates moving internal parts of the pump. When oil or solvent mixes with this graphite dust, it keeps vanes from moving freely in their slots and they stick. At low engine RPM, the vanes are recessed in their slots and create no vacuum, but as engine RPM increases, centrifugal force slings the vanes out, allowing them to grab air and create vacuum. Once a pump has become contaminated, its life expectancy is extremely short. The cause of pump contamination should be determined and
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