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Boost your knowledge; turbo fault diagnosis tips

By autotech-nic on March 21, 2023

As the latest generation of turbocharged vehicles filters into the service network, accurate diagnostics is a must for any garage. To help you, leading remanufacturer and technical expert, Carwood, give you some pointers on what to look out for and why on your next turbo related failure.

Thanks to their proven ability to improve engine efficiency and fuel economy, whilst reducing emissions, turbos can now be found in almost every type of car, providing an ever-growing parc of vehicles that will require cost-effective, high-quality repairs.

Yet despite their growing popularity, turbo failures are still often misunderstood. Faced with an issue, many will wrongly blame the turbo itself. The truth is, they are incredibly reliable; less than 1% fail due to a manufacturing defect with the actual unit, so it’s rarely the turbo, but something else. The question is what?

“Fortunately a handful of causes account for the majority of failures,” explains Will Johnson, Turbo Sales Manager, Carwood. “By taking the time to carefully evaluate the turbo’s key components and other related systems, and knowing what to look out for and why, issues can be correctly pinpointed and remedial action taken, to avoid a repeat failure.”

“Foreign object impact damage, for example, can be caused when dirt, dust, and debris from broken components or a previous failure, enters the turbine, compressor or bearing housing. At high speeds, this can result in imbalance and costly impact damage to the compressor and turbine blades. Replacing the vehicle’s air filter at regular intervals and checking the turbo for debris, worn pipework and restrictions to the air induction system is an easy way to prevent this.”

“A build-up of carbon deposits in the oil feed, blocked oil filters and the incorrect grade or quantity of oil, can starve the turbo of lubricant – its lifeblood,” he continues. “The tell-tale signs are discolouration of the shaft, excessive wear to the thrust bearing pad, an out of balance shaft and even complete shaft failure, so it’s a good idea to check and clean the entire air and oil supply system, use fresh oil, and fit new components where required.”

“The same carbon build-up can lead to oil contamination, one of the other main causes of turbo failure. As too, can a blocked/poor-quality oil filter or engine oil that’s past its best. Look out for grooves or scoring to the journal bearing, journal bearing diameters, wheel and thrust
components. Larger particles may cause internal damage to the shaft and bearing. Similar to the above, we’d recommend flushing and refilling the oil, fitting new OE-quality oil filters, and thoroughly cleaning the entire oil supply and return system.”

Admittedly, accurate diagnosis is not always straightforward, as some causes and symptoms overlap. Johnson explains: “Take a poorly routed or blocked oil return pipe; it can restrict the flow of oil out of the turbo, causing a build-up of oil pressure in the bearing housing and in turn oil leaks at both ends. The same can cause damage to the turbine side, through overheating.”

“Although discolouration of parts is more typical of oil starvation, it can indicate other problems, so, it’s important to look at the pattern for more clues. Staining that starts at the turbine wheel and continues through the shaft to the compressor side suggests excessive heat caused by increased back pressure from a DPF related issue, and not a lack of lubrication.”

These examples, highlight the need for garages to always fit top-quality parts, and follow a methodical process when doing so. Carwood can help with both. In addition to a wide range of proven quality, sustainable and cost-effective turbochargers, available from factors nationwide, it has produced a handy fault guide of the main on-vehicle symptoms, to help you quickly and accurately pinpoint possible faults, available below:

The company will also be providing more detailed insights throughout the year, so keep watching this space.

In the meantime, for further support on diagnosis, removal and refit, call Carwood’s dedicated turbo technical hotline on 01623 867966.



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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