Why Has My Turbo Failed?
In this section, we look at the common causes of turbocharger failure, how to spot a faulty turbo, and the steps to take to ensure that you don’t have the same issues arise after replacing it.
Turbochargers are extremely reliable: less than 1% of warranty inspections find a fault with the turbo itself. 95% of turbocharger failures are caused by oil contamination, oil starvation, or foreign body impact damage.
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Faulty Turbo: the major reasons for turbocharger failure
1. Oil Contamination
The turbine shaft and internal bearings of the turbocharger rotate on a thin film of oil. Contamination of this oil can degrade the surface of these crucial components and lead to the failure of the turbocharger.
Oil contamination can be caused by:
Use of oil that has passed the recommended service interval;
A poor quality, damaged, or blocked oil filter and or/filter bypass valve;
High carbon build up in the engine; and excessive engine temperatures.
When fitting a replacement turbocharger, always clean or replace oil inlet pipes, replace oil filters, and use fresh oil of the grade recommended by the engine manufacturer.
2. Oil Starvation
Oil starvation can be caused by: a bent or blocked oil feed pipe, low engine oil in the sump, a poor quality, damaged, or blocked oil filter, a blocked oil inlet gasket, and the engine not being used for long periods.
When fitting a replacement turbocharger, in addition to the above, always prime the turbocharger with fresh oil, check oil pressure in the turbocharger, and never use silicon to fix oil gaskets – it can easily detach and cause blockages.
Some turbochargers can spin at over 300,000 RPM: even the smallest foreign body in the system can destroy the compressor or turbine wheels.
Impact damage to the compressor wheel is caused by: gasket parts entering the intake, damaged air hoses, and a poor quality, damaged, or blocked air filter. Turbine wheel impact damage is generally caused by engine parts entering the exhaust system.
When fitting a replacement turbocharger, always fit a new air filter, use new gaskets, ensure that all air hoses are in good condition and free from blockages, and check that there are no foreign bodies in the system from a previous turbocharger failure.
4. Oil Leaks
Turbos rely on positive air pressure to maintain oil lubrication of the bearings and turbine shaft.
Restrictions at either compressor or turbine end can affect this air pressure and cause oil to leak, resulting in insufficient lubrication.
Ensure there are no blockages in the air, oil drainage, EGR, and exhaust systems.
Modern Turbochargers are designed to operate at defined speeds, exceeding which can damage compressor and turbine wheels. Continued overspeeding can overboost the engine, potentially leading to complete engine failure.
Restrictions in the air intake system can allow incorrect amounts of air into the turbocharger, as can a faulty wastegate or electronic actuator. A modified ECU can also lead to the turbocharger operating incorrectly.
Ensure no blockages to the air intake, and check that the wastegate and/or nozzle ring is operating correctly.
6. EGR Valve
EGR valves reduce nitrous oxide emissions by redirecting exhaust gasses back into engine cylinders.
A sooty/coked EGR valve can result in carbon build up at the turbine end, which can block the VNT mechanism.
7. Actuator Failure
Actuators regulate the vanes on a VNT turbocharger to improve response time at low speeds.
Actuator failure can result in both low boost and high boost and excessive noise from the turbocharger.
Check previous ECU error codes and replaced engine parts, particularly the EGR valve.
How to Spot a Faulty Turbocharger
There are a number of symptoms of a faulty turbo.
Loss of Power
If your vehicle is no longer capable of reaching the same speeds that it previously could, or seems to accelerate slower than before, the turbo could be the culprit.
Blue Smoke from the Exhaust
A turbo that is leaking oil will often result in the vehicle emitting a blue-grey smoke. Oil leaks into the exhaust system from a cracked turbine housing or blown internal seals on the turbocharger.
Turbo Whistle / Scream
Although all turbochargers make some noise when deployed at high RPM, if you notice a loud, high-pitched noise from the engine, the culprit might be a damaged turbocharger compressor wheel, possibly from impact damage, which could lead to more serious engine problems.