Turbocharger Failures and Indicators
Summary – Checking the Vehicle and Peripheral Systems
Turbocharger troubleshooting needs to be looked at holistically.
That is, the peripheral vehicles systems, maintenance and how initial turbocharger installation was performed.
Here are some peripheral systems to check when diagnosing a turbocharger failure:
1) Make sure all pipes and air filters are clean and seals or gaskets are air-tight.
2) Make sure all oil lines are in good condition, and free from damage (especially internally where it damage may be less obvious).
3) If a valve exists in the oil line to check oil from seeping back into the turbo, make sure that valve is operating correctly.
4) If the system has an oil scavenge pump make sure that it is operating and drawing oil correctly.
5) Where no pump exists, make sure the return oil line has its entire length sloping vertically towards the drain.
6) Make sure oil drains back to the sump unrestricted to a port that is above the level of oil in the sump and / or that the oil sump is not overfilled.
7) Similarly crankcase pressures must remain low to allow oil back in from the return line, so any blockage to the ventilation system in the crankcase may create a pressure build up.
This could force oil back up the return line and into the turbo, breaching the seals. Check that the crank case is breathing properly.
Turbocharged vehicles in particular, are more likely to develop air and gas leaks, as they have extra hoses and connections.
These fittings are subject to more heat in the engine bay, and higher pressure than a non-turbo vehicle. So they are more likely to dry and crack, or come loose.
Loose fittings or cracked pipes and split hoses, often create a ‘whistling’ noise under engine operation. The whistling or high pitch noise, is air or gas escaping under pressure, or being sucked inward under vacuum.
Comprehensive list of Failures & Indicators:
Squealing/high-pitch whistling noise from engine bay:
Possible Sources:
– Damaged compressor blades (even just a small nick).
– Split or damaged vacuum hose.
– Incorrectly operating wastegate / VNT actuator.
– EGR valve broken or seized.
– Too much resistance in air filter(clogged).
– Leaking / split Manifold flange or Dump flange gaskets.
– Piping for inter-cooler damaged or loose hose clamps.
Loose hose clamps will make engine run rich.
Excessive Oil Use: (often resulting in smoke)
Possible Sources:
– Sump too full.
– Oil drain pipe clogged forcing oil into Turbo CHRA.
– Tolerance between turbocharger shaft and bearings / piston ring too large.
– Lack of Oil Catch Can as part of Turbocharger sub-system.
– Clogged crank-case breather.
– Worn engine components – piston rings or cylinder sleeves.
Smoke (Blue-Grey):
Possible Sources:
– Worn engine components – piston rings or cylinder sleeves.
– Clogged air filter system.
– Oil sump too full.
– Flow resistance in exhaust system.
– Clogged crank-case breather.
– Oil leakage into Turbo Compressor or Turbine Housing.
Smoke (Black):
Possible Sources:
– Clogged air filter system.
– Faulty injector or fuel mix system.
– Inter cooler pipes kinked or loose hose clamp.
– Worn engine components – piston rings or cylinder sleeves.
Compressor housing leaking oil:
Possible Sources:
– Lack of Oil Catch Can as part of Turbocharger sub-system.
– Clogged crank-case ventilation.
– Faulty sealing between compressor housings havles.
– Engine oil sump too full.
– Oil pressure into Turbo oil feed line too high.
– Restricted Turbocharger oil drain pipe.
– Turbocharger shaft & bearings / piston rings tolerance too large.
Oil leaking from the turbine:
Possible Sources:
– Clogged crank-case ventilation.
– Engine oil sump too full.
– Oil pressure into Turbo oil feed line too high.
– Oil drain pipe clogged forcing oil into Turbo CHRA.
– Flow resistance in the exhaust system.
– Turbocharger shaft & bearings / piston rings tolerance too large.
Low Boost Pressure / Power:
Possible Sources:
– Actuator & boost control solenoid hose leaks.
– Damaged bearings inside Turbocharger.
– Clogged air filter system.
– FOD to impeller or turbine blades.
– Flow resistance in exhaust system.
– Boost pressure control valve seized open.
Over-boost / Pressure too high:
Possible Sources:
– Actuator & boost control solenoid hose leaks.
– Pipes for intercooler split or hose clamps loose.
– Boost pressure control valve seized in closed position.
– Damaged diaphragm in vacuum actuator.
– Calibration of Wastegate / Electric Actuator out of range.
Damage to Impeller / Turbine:
Possible Sources:
– Ineffective air filtering allowing particulates through.
– Impeller lock-nut spun off due to over-speeding or sudden stop of shaft rotation.
– Bearing damage inside Turbo.
For more information on why Turbochargers fail, please see this link to Garrett on “Why Turbochargers Fail” (Garrett is the world’s largest Turbocharger manufacturer).
Hope our Turbocharger Failures and Indicators list has helped in some way. But as always, this is just a guide.
Proper diagnosis by a qualified mechanic is always required to find the exact nature of any turbocharger problem.
