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Turbo clinic

By autotech-nic on January 14, 2016

Turbochargers are commonplace now as VMs squeeze more power out of smaller engines but can be a challenge to repair.

Forced induction to maximise engine performance has been a growing trend for vehicle manufacturers (VMs) for some time, but even though they are therefore commonplace, turbochargers still represent a challenge to many independents undertaking their service or repair.

For this reason, original equipment (OE) component and systems manufacturer MAHLE, has issued the following technical information to highlight some common causes and effects of turbocharger damage.

Damage to the turbine is one of the primary reasons behind poor turbo performance, or even complete component failure and contamination of some form is generally responsible.

Oil matters

If oil carbon enters the bearing case, (image 1) it can result in any or all of the following: blue smoke, the loss of engine performance, the loss of engine oil, contamination of the charge-air cooler, clogged exhaust gas cleaning system and with adjustable turbochargers, blocked control mechanisms.


Image 1

Generally these effects are caused by poor quality engine oil, an overheating turbo or the immediate shut down of a hot engine. Therefore it is vital to use the correct grade of oil as specified by the VM and let a hot engine run for at least a minute before shutting it down.

In addition, technicians must thoroughly clean the oil pan, and flush the oil following turbocharger damage to ensure that no foreign deposits enter the lubrication circuit and pay close attention to the necessary installation instructions and performance measures during engine tuning.

Naturally, observing the VM’s oil change intervals and replacing the filter with an OE replacement is a prerequisite. Oil carbon deposits in the oil pipe (image 2) can have similar effects to oil carbon found in the bearing case, but can also lead to excessive turbocharger noise and even total turbocharger failure.

Image 2

The additional causes include an overdue oil change, incorrectly installed oil pipe or missing heat shield. The subsequent additional remedies include replacing the oil pipe and ensuring its correct installation and replacing the charge-air cooler and particulate filter if the turbocharger has needed replacement.

Excessive oil consumption can often be due to a problem with the oil return pipe (image 3), which in common to the aforementioned oil related issues, means that oil can be forced into the turbine and the compressor, which can affect the operation of the internal components and can collect in the charge-air cooler.

Image 3

Image 3







Probable causes include constriction or a bend in the oil return pipe, the use of sealing compound rather than a gasket set, the failure to replace the engine connection when replacing the return pipe, or even simply too much oil in the engine.

Technicians therefore need to ensure that the return pipe is thoroughly cleaned if it is to be reused and whether reinstalled or replaced, a new gasket set must be used. In addition, the turbo must be replaced if any its internal components (VTG, by-pass, waste gate etc.) have become stiff.

Compressor Related Problems

When it comes to the air intake side of the equation, contamination of, or stress to, the compressor wheel or compressor itself will result in blue smoke – or black in the case of stress marks on the compressor wheel – excessive noise (whistling) and contamination in the charge-air cooler.

The causes can vary, but can include contamination entering the system from the crankcase vent (image 4), a build up of ice or even a leak in the system from, for example, a split turbo hose.

Image 4

Image 4








When it comes to the compressor wheel (image 5), stress is general caused by dirty or deficient oil to the bearing, an increase in exhaust back pressure or a clogged air filter.

Image 5

Image 5

To remedy these situations, technicians must carefully clean the entire intake system, replace the air filter with an OE replacement, clean or renew the crankcase vent and check the system for leaks. In addition, if fitted, the air compressor’s cylinder head must be dismantled and cleaned and flowing the replacement of the turbocharger and charge-air cooler, the mass air flow sensor must be checked.

If the compressor wheel bearing is damaged (image 6), its clearance on the rotor shaft must be checked, the engine oil flushed and a new OE filter fitted with the addition of the correct grade of engine oil as specified by the VM.

Image 6

Image 6


For more information about the quality products available from MAHLE Aftermarket, call the sales team on: 0845 688 5007 or visit:




About Autotechnician
Autotechnician is a magazine published nine times a year, delivering essential information to independent garage owners and technicians in the UK. Delivered both digitally and in print, autotechnician provides readers with technical, training, business advice, product and news, allowing our readers to keep up to date with information they need to run and work within a modern workshop.
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