OIL CONTAMINATION

What causes oil contamination?

• If the oil filter is blocked/damaged or a poor quality oil filter is used
• Excess moisture can lead to premature oil degradation
• High carbon build up in the engine can quickly contaminate new oil

Alternatively, if oil levels are too low or if the wrong grade of oil is used, the turbocharger can prematurely fail.

Turbo failure prevention:

• Using new oil and filters helps to reduce the risk
• Replacement oil must be the correct grade for the engine
• Replacing or cleaning the oil inlet pipes and in-line micro filters

Signs of oil contamination:

Scoring to the journal bearing diameter of the shaft

Scoring to thrust parts

Scoring to journal bearings

OVERSPEEDING

What causes overspeeding?

• Poor boost control in the ECU software (bad tuning)
• Over-fuelling which then causes boost creep at higher RPMs
• Inconsistent flow of air into the turbo - this can be caused by a hole in the air hose or it becoming completely detached, or by restrictions in the air intake filter or pipe work
• Intercooler pipework leaks - The Pressure sensor is AFTER the Intercooler
• The wastegate or VNT mechanism has been set incorrectly
• Worn injectors
• Installing an incorrect turbo
• Loss of signal to the SREA (Simple Rotary Electronic Actuator) for the wastegate or VNT control

Signs of overspeeding:

Complete component failure

Orange peel effect to compressor wheel

Compressor wheel rubs

OIL STARVATION

What causes of a lack of lubrication or oil starvation?

• Poor oil filter maintenance
• Insufficient oil in the sump
• Incorrect oil inlet gasket used, leading to restriction in oil supply
• A damaged, blocked or low quality oil filter

Turbo failure prevention:

• Turbo oil supply is critical, always check oil pressures are correct
• Avoid using silicone on oil gaskets as they can easily become detached and block oil passages
• Clean or replace oil inlet pipes to remove carbon deposits or sludge

Signs of oil starvation:

Material transfer from journal bearing

Discolouration to the journal bearing diameter of the shaft

Excessive wear to thrust bearing

Signs of oil leaks:

• Blue smoke from the exhaust
• Oil residue in compressor/turbine housings

Causes of oil leaks at the compressor end:

• Blockages or restrictions to the air intake pipe, hose or air intake filter can create a vacuum, causing oil to leak into the compressor housing
• Air leaks in the intake hoses or at the intercooler

Causes of oil leaks at the turbine end:

• Leaks within the exhaust system
• A clogged bearing housing
• Leaks in the EGR (exhaust gas recirculation) system

Causes of oil leaks into the compressor and turbine ends:

• Repeated hot engine shutdowns leading to carbon deposits (coke) in the centre housing
• Physical damage to the turbo’s rotating parts and excessive bearing clearance
• Fitting the incorrect turbocharger
• Restrictions in the oil return pipe

Turbo failure prevention:

• Ensure air and oil drain systems are clear from blockages or restrictions
• Check the exhaust system to make sure there are no leaks present
• Ensure DPF and Catalytic converter are free of blockages