Oil leaks can cause catastrophic damage to the bearing systems and occur within seconds of the turbocharger commencing operation.Turbochargers can spin at over 240,000 rpm and endure temperatures of 950°C.
The turbo relies on the thin film of oil that lubricates the bearings on the turbine shaft. This oil is kept in place by seals for the turbine and compressor ends of the bearing housing.Compressing air creates large amounts of heat, therefore turbochargers have multiple oil and coolant passages running through them to lubricate and cool the moving parts in the turbo.
Seals throughout the turbo keep these fluids from leaking into the air intake of the engine.These seals are unlike conventional oil seals, and similar to piston rings. They need positive air pressure inside the compressor and turbine to keep oil lubricating the bearings and prevent it seeping into the end housings.
A restriction on the inlet side will create a vacuum that will pull oil past the seals at the compressor end housing. If the engine idles for long periods, the turbo will rotate at very low speed with correspondingly low air pressure. The resulting vacuum will cause oil to seep into the turbine housing. Either situation results in insufficient oil for the turbine bearings.