The turbo makes a noise or loses power: early signs of turbo failure and proper diagnosis in Espoo

Early signs of a turbo failure may manifest as a new whine, a loss of power, black smoke from the exhaust or the engine entering fault mode. However, these symptoms do not necessarily mean that the turbocharger is faulty. The same driving sensation can be caused by a cracked turbo hose, a leaking intercooler, a fault in the vacuum control system, or a pressure sensor providing incorrect data.

You should not continue to drive the car under heavy loads until the cause has been identified. An early inspection may pinpoint the fault as being a relatively inexpensive hose or joint. If the fault lies with the turbocharger, a timely repair will minimise the risk of further damage to the engine and exhaust system.

Early signs of a turbo failure: a whining noise and a change in the engine sound

When operating, the turbocharger emits a faint whistling sound, which becomes louder as the boost pressure rises. You should be alert to any noise that has not previously been heard in the car. A high-pitched whine, howl, metallic grinding or a sound resembling a siren may be related to the turbo’s bearings, the compressor wheel or a leak in the boost piping. The nature of the sound and the moment it occurs will help to pinpoint the cause.

A cracked turbo hose allows pressurised air to escape and often produces a hissing or loud whooshing sound during acceleration. A leak in the exhaust manifold or on the exhaust side of the turbocharger, on the other hand, may sound like a ticking or rattling noise. At the garage, the noise is investigated not only during a test drive but also from inside the engine compartment, as the sound reaching the driver’s seat can be misleading.

A loss of power does not necessarily mean the turbo has broken down

A lack of boost pressure usually results in sluggish acceleration. The engine may perform reasonably well at low revs but struggle when overtaking or going uphill. In a diesel car, fuel consumption may increase, and the exhaust may emit darker smoke than usual. In a petrol engine, an incorrect air-fuel ratio may cause rough idling or trigger fault codes related to mixture adjustment.

Before replacing the turbo, the entire turbocharging system must be checked. A loose hose connection, a cracked pipe or a leaking intercooler can reduce boost pressure, even if the turbo is producing pressure normally. A blocked air filter, back pressure in the exhaust system or a jammed turbo control mechanism can also affect the engine’s airflow.

A mere feel for the engine is not enough to tell whether the required boost pressure is being generated. During a test drive, the mechanic compares the pressure requested by the engine control unit with the measured pressure, whilst also checking the air mass, the operation of the control valve and the load. This ensures that the turbo is not replaced due to a fault caused by a crack of just a few centimetres in a hose.

You should only rule out a turbo fault once the integrity of the boost piping, the control system and the readings have been checked.

Early signs of turbo failure: oil leak, smoke and high oil consumption

The turbocharger requires engine oil to lubricate and cool its bearings. Oil may be visible around the turbocharger due to an external leak, but a thin film of oil in the intake-side pipes does not in itself indicate a turbocharger fault. The crankcase ventilation system carries oil mist into the intake system, which accumulates on the surfaces of the pipes over time.

Excessive oil in the turbocharger piping, a rapidly falling oil level or bluish exhaust fumes require investigation. The cause may be play in the turbo shaft or damage to the seal, but a blockage in the venting system, an excessively high oil level or a fault in the turbo’s oil return pipe may also cause oil to be forced in the wrong direction. You can read more on this topic an article on fuel consumption and exhaust fumes.

The fault may be caused by a hose, the vacuum control system or a sensor

The engine control unit may limit power if the measured boost pressure deviates from the set value. In a vacuum-controlled system, a brittle hose, a leaking vacuum bellows or a faulty control valve will prevent the turbo blades or wastegate from moving correctly. In an electronically controlled turbo, the fault may lie with the actuator, the wiring or a connector.

The MAP sensor measures the pressure in the intake manifold, and the air flow meter indicates the volume of air flowing into the engine. A dirty or faulty sensor may provide data that appears credible but is in fact incorrect. The significance of the engine warning light and safe operating procedures are discussed in more detail in the guide on the engine warning light.

Garrett, a turbocharger manufacturer, emphasises in its own in its guide on turbocharger troubleshooting, …that, when investigating performance issues, the engine’s other systems must also be checked. Replacing the turbocharger without first identifying the cause of the original fault may result in the new part being damaged in the same way.

Proper turbo troubleshooting for a car arriving from the Espoo area

A systematic inspection begins with the customer’s observations, a check of the oil level and the reading of fault codes. Next, the mechanic checks the air intake and boost pipes, hose connections, the intercooler and the turbo for external oil and exhaust leaks. The engine’s service history helps to assess whether the wrong grade of oil, long oil change intervals or inadequate air filtration may have caused damage to the turbocharger.

During the test run, the mechanic records the requested and actual boost pressure, air mass and turbo control values. If necessary, they carry out a pressure or smoke test on the turbo system and check the turbo shaft play in accordance with the manufacturer’s instructions. Only after these measurements have been taken can a decision be made as to whether replacing a hose, valve or sensor will suffice, or whether the turbo needs to be repaired or replaced.

STS Evitskog has been serving motorists in the Espoo, Veikkola, Siuntio and Kirkkonummi areas for over 20 years. The garage is located at Kylmäläntie 350, 02540 Kirkkonummi. When you book an appointment, please mention any noises, smoke, warning lights or instances of power loss, so that the garage can allocate a suitable time slot and the appropriate equipment for the diagnosis.